Attenuation of Light Transmittance Artifacts in Wearable Displays

Abstract

The wearable display system includes an eyepiece stack having a world side and a user side opposite the world side, and during use, positioned on the user side, a user views displayed images delivered by the system through the eyepiece stack that augment the user's view of the user's environment. The wearable display system also includes an angularly selectable film arranged on the world side of the eyepiece stack. The angularly selectable film includes 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 large angles of incidence without significantly reducing the transmittance of light incident on the angularly selectable film at small angles of incidence.

Description

[Technical field]

[0001] The present disclosure relates to techniques for attenuation of light transmission artifacts in wearable displays. [Background technology]

[0002] An optical imaging system, such as a wearable display system (e.g., a wearable display headset), can include one or more eyepieces that present a projected image to a user. The eyepiece can be constructed using one or more thin layers of highly refractive materials. As an example, the eyepiece can be constructed from one or more layers of highly refractive glass, silicon, metal, or polymer substrates.

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

[0004] Optical elements in a wearable display system may also interact with ambient light, which is light from the environment the user is in. For example, diffractive structures in a wearable display system may diffract ambient light that is incident on the wearable display at high angles that would not normally enter the user's field of view into the field of view creating visible artifacts that diminish the user's experience. Summary of the Invention [Means for solving the problem]

[0005] A wearable display system is described that includes an angularly selectable film and reduces artifacts associated with ambient light incidence at high angles of incidence. For example, the angularly selectable film can utilize a polarizer in combination with a polarization adjustment element, where the amount of adjustment varies depending on the angle of incidence of the light, to reduce the transmission of light at certain angles of incidence. In some embodiments, the angularly selectable film can include a dynamic element in which the transmission 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 invention features a wearable display system including an eyepiece stack having a world side and a user side opposite the world side, where during use, a user views displayed images delivered by the wearable display system through the eyepiece stack that extend the user's field of view of the user's environment. The wearable display system also includes an angularly selectable film arranged on the world side of the eyepiece stack, the angularly selectable film including a polarization adjustment film arranged between a pair of linear polarizers, the linear polarizers and the polarization adjustment film significantly reducing the transmission of visible light incident on the angularly selectable film at large angles of incidence without significantly reducing the transmission of light incident on the angularly selectable film at small angles of incidence.

[0007] Embodiments of the wearable display system can include one or more of the following features and / or features of other aspects. For example, the pass axes of the two linear polarizers can be crossed.

[0008] In some embodiments, the 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 can be rotated less than light transmitted with a small angle of incidence.

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

[0010] Unpolarized light with wavelengths in the range of 420 nm to 680 nm incident on the angularly selectable film with angles of incidence of -32° to +32° can have a transmission efficiency of greater than 45%.

[0011] For a D65 source, the angularly selectable film can shift the CIE 1931 white point by less than (+ / -0.02, + / -0.02) (0.33, 0.33) for unpolarized light with angles of incidence from -32° to +32°.

[0012] Angularly selectable films are larger than 10 mm x 10 mm (e.g., 2,500 mm 2 or larger (e.g., larger than 50 mm x 50 mm), such as 200 mm 2 or more, 500mm 2 or more, 1,000 mm 2 or greater).

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

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

[0015] The polarization adjusting film can be a first polarization adjusting film, and the angularly selectable film can further include a second polarization adjusting film and a third linear polarizer, with the second polarization adjusting film arranged between the pair of linear polarizers and the third linear polarizer. The first and second polarization adjusting films can each be composed of one or more layers of birefringent material. The one or more layers of birefringent material of the first and second polarization adjusting films can each include a C-plate. The one or more layers of birefringent material of the first and second polarization adjusting films can each include a pair of quarter wave plates arranged on opposite sides of the corresponding C-plate.

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

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

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

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

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

[0021] Directing the display light may include guiding the display light through a waveguide in the eyepiece and diffracting the guided display light towards a user.

[0022] The method can include varying an attenuation of the transmitted ambient light in response to a signal from the wearable display system. For example, the attenuation can be varied by different amounts across the eyepiece. 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 certain wearable displays associated with stray ambient light interacting with grating structures in the display. For example, waveguide-based wearable displays (e.g., for AR / MR applications) employing surface relief gratings can diffract stray ambient light into the display's eyebox, resulting in undesirable artifacts in the user's field of view and diminishing the user's 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 for angles of incidence greater than the user's field of view can reduce the visibility of artifacts produced by a diffractive eyepiece display without sacrificing transmittance of the user's view of the world.

[0025] The 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. The present specification also provides, for example, the following items: (Item 1) A wearable display system, comprising: an eyepiece stack having a world side and a user side opposite the world side, wherein during use, a user positioned on the user side views through the eyepiece stack displayed images that extend the user's field of view of the user's environment delivered by the wearable display system; an angularly selectable film arranged on a world side of the eyepiece stack, the angularly selectable film comprising a polarization adjustment film arranged between a pair of linear polarizers; Equipped with A wearable display system, wherein the linear polarizer and polarization adjusting film significantly reduce the transmittance of visible light incident on the angularly selectable film at large angles of incidence without significantly reducing the transmittance of light incident on the angularly selectable film at small angles of incidence. (Item 2) Item 2. The wearable display system of item 1, wherein the pass axes of the two linear polarizers are crossed. (Item 3) 3. The wearable display system of claim 1 or 2, wherein the polarization adjusting film rotates the polarization state of light transmitted by a first linear polarizer of the pair of linear polarizers on the world side of the polarization adjusting film. (Item 4) 4. The wearable display system of claim 3, wherein the amount of rotation of the polarization state varies depending on the angle of incidence of light transmitted by a first linear polarizer of the pair of linear polarizers. (Item 5) 5. The wearable display system of 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) The wearable display system of any of the preceding items, wherein unpolarized light with a wavelength 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) The wearable display system of any of the preceding items, wherein unpolarized light with a wavelength 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 greater than 45%. (Item 8) The wearable display system of any of the preceding items, wherein for a D65 source, the angularly selectable film shifts the CIE 1931 white point by less than (+ / -0.02, + / -0.02) for unpolarized light with an incidence angle of -32° to +32° (0.33, 0.33). (Item 9) 2. The wearable display system of any of the preceding items, wherein the angularly selectable film has an area greater than 50 mm x 50 mm. (Item 10) 2. The wearable display system of any of the preceding items, wherein the polarization adjusting film comprises at least one layer of birefringent material. (Item 11) Item 11. The wearable display system of item 10, wherein at least one layer of birefringent material comprises a C-plate. (Item 12) Item 12. The wearable display system of item 11, wherein at least one layer of birefringent material comprises a pair of quarter-wave plates, the quarter-wave plates being positioned on opposite sides of the C-plate. (Item 13) Item 13. The wearable display system of item 12, wherein each quarter-wave plate is aligned with a corresponding one of the linear polarizers to form a circular polarizer. (Item 14) Item 12. The wearable display system of item 11, wherein at least one layer of birefringent material comprises at least one quarter wave plate. (Item 15) The wearable display system of any of the preceding items, 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. (Item 16) Item 16. The wearable display system of item 15, wherein the first and second polarization adjusting films each consist of one or more layers of birefringent material. (Item 17) Item 17. The wearable display system of item 16, wherein the one or more layers of birefringent material of the first and second polarization adjusting films each comprise a C-plate. (Item 18) Item 18. The wearable display system of item 17, wherein the one or more layers of birefringent material of the first and second polarization adjusting films each comprise a pair of quarter-wave plates arranged on opposite sides of the corresponding C-plate. (Item 19) The wearable display system of any of the preceding 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) 20. The wearable display system of item 19, wherein adjacent stages share a linear polarizer. (Item 21) 2. The wearable display system of claim 1, wherein the angularly selectable film further comprises a switchable element having variable optical properties. (Item 22) 22. The wearable display system of claim 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) 22. The wearable display system of claim 21, wherein the switchable element comprises a plurality of pixels, the optical properties of each pixel being independently variable. (Item 24) 1. A method for displaying an image using a wearable display system, comprising: directing display light from a display towards a user through an eyepiece to project an image into a field of view of said user; transmitting ambient light from the user's environment through the eyepiece; Including, The method, wherein transmitting the ambient light includes attenuating light incident on the eyepiece from the environment as a function of the angle of incidence of the ambient light on the eyepiece, such that ambient light incident on the eyepiece at an angle of incidence of 35° or greater is attenuated more than ambient light incident on the eyepiece at an angle of incidence of 35° or less. (Item 25) 25. The method of claim 24, wherein attenuating the ambient light comprises polarizing the ambient light, providing polarized light, and modulating a polarization state of the polarized light as a function of an angle of incidence of the ambient light. (Item 26) 26. The method of claim 25, wherein modulating the polarization state of the polarized light comprises rotating the polarization state. (Item 27) 27. The method of claim 26, wherein the amount of rotation of the polarization state varies depending on the angle of incidence of the ambient light. (Item 28) 28. The method of claim 27, wherein the amount of rotation decreases as the angle of incidence increases. (Item 29) Item 26. The method of item 25, wherein attenuating the ambient light further comprises directing the polarized light through a second polarizer. (Item 30) 25. The method of claim 24, wherein the ambient light transmittance is 1% or less for at least one angle of incidence greater than 35°. (Item 31) 31. The method of claim 30, wherein the ambient light transmittance is 1% or less for at least one angle of incidence greater than 50°. (Item 32) Item 31. The method of item 30, wherein the ambient light transmittance is 1% or less for at least one angle of incidence within a range of 60° to 80°. (Item 33) 33. The method of 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) 33. The method of any 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) Item 35. The method of item 34, wherein the attenuation is varied by different amounts across the eyepiece. (Item 36) 35. The method of claim 34, wherein the attenuation is varied using a liquid crystal element. [Brief description of the drawings]

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

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

[0028] [Figure 2B] FIG. 2B illustrates aspects of an approach for simulating a three-dimensional image using multiple depth planes.

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

[0030] [Figure 4] FIG. 4 shows an embodiment of a waveguide stack for outputting image information to a user in an AR eyepiece.

[0031] [Diagram 5] 5 and 6 show examples of output beams output by waveguides. [Figure 6] 5 and 6 show examples of output beams output by waveguides.

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

[0033] [Figure 8] 8A and 8B are schematic diagrams partitioning light transmission through a display combiner with and without an angularly selectable film.

[0034] [Figure 9]FIG. 9 is a schematic diagram of an eyepiece with a display combiner and an embodiment of an angularly selectable film.

[0035] [Figure 10] FIG. 10 is a plot showing transmission as a function of incident light angle through examples of angularly selectable films.

[0036] [Figure 11] FIG. 11 is a schematic diagram of an eyepiece with a display combiner and another embodiment of an angularly selectable film.

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

[0038] [Figure 13] FIG. 13 is a schematic diagram of an eyepiece with a display combiner and an embodiment of an angularly selectable film that includes a segmented dimmer.

[0039] [Figure 14] FIG. 14 is a schematic diagram of an eyepiece with a display combiner and another embodiment of an angularly selectable film that includes a segmented dimmer.

[0040] [Figure 15] FIG. 15 is a schematic diagram of an eyepiece with a display combiner and yet a further example of an angularly selectable film that includes a segmented dimmer.

[0041] [Figure 16] FIG. 16 is a schematic diagram of an exemplary computer system useful in conjunction with a wearable display system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Detailed Description FIG. 1 illustrates an exemplary wearable display system 60 including 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 90 eye. The display 70 may be considered eyewear in some embodiments. In some embodiments, a speaker 100 is coupled to the frame 80 and positioned adjacent to the ear canal of the user 90. The display system may also include one or more microphones 110 to detect sound. The microphone 110 may enable the user to provide input or commands to the system 60 (e.g., voice menu command selections, natural language questions, etc.) and / or enable audio communication with other persons (e.g., other users of a similar display system). The microphone 110 may 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 an ambient sensor 120a, which may be separate from the frame 80 and attached to the body of the user 90 (e.g., on the head, torso, limbs, etc.). The ambient sensor 120a, in some embodiments, may acquire data characterizing a physiological state of the user 90.

[0043] The display 70 is operably coupled by a communication link 130, such as wired or wireless connectivity, to a local data processing module 140, which may be mounted in a variety of configurations, such as fixedly attached to the frame 80, fixedly attached to a helmet or hat worn by the user, built into headphones, or otherwise removably attached to the user 90 (e.g., in a backpack configuration or in a belt-connected configuration). Similarly, the sensor 120a may be operably coupled to the local processor and data module 140 by a communication link 120b (e.g., wired 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 hard disk drive), both of which may be utilized to aid in processing, caching, and storing data. The data may include 1) data captured from sensors (e.g., which may be operatively coupled to the frame 80 or otherwise attached to the user 90), 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, 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), possibly for passing to the display 70 after processing or retrieval. The local processing and data module 140 may be operatively coupled to the remote processing module 150 and the remote data repository 160 by communication links 170, 180, such as via wired or wireless communication links, such that these remote modules 150, 160 are operatively coupled to each other and available as resources to the local processing and data module 140.In some embodiments, 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 frame 80 or may be stand-alone devices that communicate with local processing and data module 140 by wired or wireless communication paths.

[0044] Remote processing module 150 may include one or more processors for analyzing and processing data such as image and audio information. In some embodiments, 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, remote data repository 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 calculations are performed in the local processing and data module, allowing for fully autonomous use from the remote modules.

[0045] The perception of an image as "three-dimensional" or "3-D" may be achieved by providing a slightly different presentation of the image to each eye of a user. FIG. 2A illustrates a conventional display system for simulating three-dimensional image data for a user. Two distinct images 190, 200, one for each eye 210, 220, are output to the user. The images 190, 200 are spaced apart from the eyes 210, 220 by a distance 230 along an optical or z-axis parallel to the user's line of sight. The images 190, 200 are flat and the eyes 210, 220 may focus on the images by assuming a single accommodated state. Such a 3-D display system relies on the human visual system to combine the images 190, 200 and provide a perception of depth and / or scale of the combined image.

[0046] However, the human visual system is complex and it is difficult to provide a realistic perception of depth. For example, many users of conventional "3-D" display systems find such systems uncomfortable or may not perceive any sense of depth at all. Objects may be perceived as "three-dimensional" due to a combination of vergence-divergence and accommodation. The vergence-divergence movement of the two eyes relative to one another (e.g., the rotation of the pupils so that the pupils move toward or away from one another, converging the eyes' individual gazes and fixating on an object) is closely linked to the focusing (or "accommodation") of the eye's lenses. Under normal conditions, a change in the focus of the eye's lenses or accommodation of the eye to change focus from one object to another at a different distance will automatically produce a matching change in vergence-divergence at the same distance, a relationship known as the "accommodation-vergence-divergence reflex" and pupil dilation or constriction. Similarly, under normal conditions, changes in vergence-divergence will induce matching changes in accommodation of lens shape and pupil size. As described herein, many stereoscopic or "3-D" display systems display a scene using a slightly different presentation (and therefore a slightly different image) to each eye so that a three-dimensional perspective 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 accommodated state and work against the "accommodation-vergence-divergence reflex." Display systems that provide a better match between accommodation and vergence-divergence may produce a more realistic and comfortable simulation of three-dimensional image data.

[0047] FIG. 2B illustrates aspects of an approach for simulating three-dimensional image data using multiple depth planes. With reference to FIG. 2B, the eyes 210, 220 assume different accommodated states and focus objects at various distances along the z-axis. As a result, a particular accommodated state may be said to be associated with a particular one of the illustrated depth planes 240 having an associated focal length such that an object or part of an object at a particular depth plane is in focus when the eye is in an accommodated state relative to that depth plane. In some embodiments, three-dimensional image data may be simulated by providing different presentations of images for each eye 210, 220 and by providing different presentations of images corresponding to multiple depth planes. Although the individual fields of view of the eyes 210, 220 are shown as separate for clarity of illustration, they may overlap, for example, as the distance along the z-axis increases. Additionally, for ease of illustration, the depth plane is shown as being flat, however, it should be understood that the contours of the depth plane may be curved in physical space such that all features within the depth plane are in focus with the eye in a particular accommodated state.

[0048] The distance between an object and the eye 210 or 220 may also change the amount of divergence of light from that object as viewed by that eye. Figures 3A-3C illustrate the relationship between distance and divergence of light rays. The distance between the object and the eye 210 is represented in the order of decreasing distances R1, R2, and R3. As shown in Figures 3A-3C, 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 (an object or part of an object) may be said to have a spherical wavefront curvature that is a function of the distance the point is away from the user's eye. The curvature increases with decreasing distance between the object and the eye 210. As a result, at different depth planes, the divergence of the light rays is also different, and the divergence increases with decreasing distance between the depth plane and the user's eye 210. Although only a monocular 210 is illustrated in FIGS. 3A-3C and other figures herein for clarity of illustration, it should be understood that the discussion regarding eye 210 may apply to both eyes 210 and 220 of a user.

[0049] A highly realistic simulation of perceived depth may be achieved by providing the eyes with different presentations of an image corresponding to each of a limited number of depth planes. The different presentations may be focused separately by the user's eyes, thereby serving to provide depth cues to the user based on the amount of ocular accommodation required to focus on different image features for a scene located on the different depth planes and / or based on the observation of different image features on the different depth planes that are out of focus.

[0050] FIG. 4 illustrates an example of a waveguide stack for outputting image information to a user in an AR eyepiece. Display system 250 includes a stack of waveguides or stacked waveguide assembly 260 that may be utilized to provide a three-dimensional perception to the eye / brain using multiple waveguides 270, 280, 290, 300, 310. In some embodiments, display system 250 is system 60 of FIG. 1, with FIG. 4 diagrammatically illustrating some portions of system 60 in greater detail. For example, waveguide assembly 260 may be part of display 70 of FIG. 1. It should be understood that display system 250 may be considered a light field display in some embodiments.

[0051] The waveguide assembly 260 may also include a number of features 320, 330, 340, 350 between the waveguides. In some embodiments, the features 320, 330, 340, 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or the number of lenses 320, 330, 340, 350 may be configured to transmit image information to the eye with various levels of wavefront curvature or light beam divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. The image input devices 360, 370, 380, 390, 400 may act as light sources for the waveguides and may be utilized to input image information into the waveguides 270, 280, 290, 300, 310, each of which may be configured to distribute incident light across each respective waveguide for output towards the eye 210, as described herein. Light exits an output surface 410, 420, 430, 440, 450 of each respective image input device 360, 370, 380, 390, 400 and is input into a corresponding input surface 460, 470, 480, 490, 500 of the respective waveguide 270, 280, 290, 300, 310. In some embodiments, each of the input surfaces 460, 470, 480, 490, 500 may be an edge of the corresponding waveguide or may be a portion of a major 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 launched into each waveguide, replicated by refraction within the waveguide, such as by sampling into beamlets, and then directed towards the eye 210 with an amount of refractive power corresponding to the depth plane associated with that particular waveguide. In some embodiments, a single one of the image launch devices 360, 370, 380, 390, 400 may be associated with and launch light into multiple (e.g., three) waveguides 270, 280, 290, 300, 310.

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

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

[0054] In some embodiments, light projector system 520 or one or more components thereof may be attached to frame 80 (FIG. 1). For example, light projector system 520 may be part of an temple portion (e.g., ear piece 82) of frame 80 or disposed at an edge of display 70. In some embodiments, light module 530 may be separate from BS 550 and / or light 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 scan, spiral scan, Lissajous pattern, 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 injection devices 360, 370, 380, 390, 400 may represent diagrammatically 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 represent diagrammatically multiple scanning fibers or multiple bundles of scanning fibers, each configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. One or more optical fibers may transmit light from the optical module 530 to one or more of the waveguides 270, 280, 290, 300, and 310. Additionally, one or more intervening optical structures may be provided between the scanning fiber or fibers and the one or more of the waveguides 270, 280, 290, 300, 310, for example, to redirect light exiting the scanning fiber into the one or more of the waveguides 270, 280, 290, 300, 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 light 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-transitory medium) that coordinates the timing and provision 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. The controller 560 may be part of the processing module 140 or 150 (FIG. 1) in some embodiments.

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

[0058] Each waveguide 270, 280, 290, 300, 310 may output light and form an image corresponding to a particular depth plane. For example, the 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 a slight convex wavefront curvature to the collimated beam so that the eye / brain interprets the light originating from that waveguide 280 as originating from the first focal plane, which is closer inward from optical infinity towards 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 add another incremental amount of wavefront curvature such that the eye / brain interprets the light originating from the third waveguide 290 as originating from a second focal plane that is closer inward from optical infinity than was the light from the second waveguide 280.

[0059] The other waveguide layers 300, 310 and lenses 330, 320 are similarly configured, with the highest waveguide 310 in the stack sending its output through all of the lenses between it and the eye for an aggregate focal power that represents the focal plane closest to the person. To compensate the stack of lenses 320, 330, 340, 350 when viewing / interpreting light originating from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be placed on top of the stack to compensate for the aggregate refractive power of the lower lens stacks 320, 330, 340, 350. Such a configuration provides as many perceived focal planes as there are waveguide / lens pairs available. Both the outcoupling 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, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may output images set at the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 may output images set at the same depth planes, with one set per depth plane. This may provide the advantage of forming tiled images to provide an extended field of view at those depth planes.

[0061] The outcoupling optical elements 570, 580, 590, 600, 610 may be configured to redirect light from its respective waveguide and output the light with an appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides with different associated depth planes may have different configurations of outcoupling optical elements 570, 580, 590, 600, 610 that 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 solid or surface features that may be configured to output light at specific angles. For example, the light extraction optical elements 570, 580, 590, 600, 610 may be solid holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 may not be lenses. Rather, they may simply be spacers (eg, cladding layers and / or structures to form an air gap).

[0062] In some embodiments, the outcoupling optical elements 570, 580, 590, 600, 610 are diffractive features with a sufficiently low diffraction efficiency such that only a portion of the optical power of the light in the beam is redirected towards 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 carrying image information from the light source 530, effectively expanding the number of locations where the eye 210 can see the replicated light source exit pupil. These diffractive 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 diffractive 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, a switchable diffractive feature may include a layer of polymer dispersed liquid crystal in which microdroplets comprise a diffractive pattern in a host medium, and the refractive index of the microdroplets 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 microdroplets may be switched to a refractive index 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, for example, detect user input, extract biometric information from the eye, estimate and track the eye's gaze direction, monitor the user's physiological condition, 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 may then be reflected by the eye and 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 the frame 80 (FIG. 1) and may be in electrical communication with a processing module 140 or 150, which may process image information from the camera assembly 630 and make various determinations regarding, for example, the user's physiological condition, the wearer's gaze direction, iris identification, etc. In some embodiments, one camera assembly 630 may be utilized per eye to monitor each eye separately.

[0065] FIG. 5 illustrates an example of an output beam output by a waveguide. Although one waveguide is shown (with a perspective view), other waveguides in the waveguide assembly 260 (FIG. 4) may function similarly. Light 640 is launched into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. Through interaction with diffractive 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 output beams 650 would be equal to the energy of the input light 640. The exit beam 650 is illustrated in FIG. 6 as being approximately parallel, but as discussed herein, a certain amount of refractive power may be imparted depending on the depth plane associated with the waveguide 270. A parallel exit beam may refer to a waveguide with an outcoupling optical element that outcouples light and forms an image that appears to be set on a depth plane at a long distance (e.g., optical infinity) from the eye 210. Other sets of waveguides or outcoupling optical elements may output an exit beam pattern that is more divergent, as shown in FIG. 6, which would require the eye 210 to accommodate to a closer distance and focus on the retina, and would be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0066] Additional information regarding wearable display systems (including, for example, optical elements used within wearable display systems) can be found in U.S. Patent Publication No. US2019 / 0187474A1, filed December 14, 2018, and entitled "EYEPIECES FOR AUGMENTED REALITY DISPLAY SYSTEM," the contents of which are incorporated by reference in their entirety.

[0067] As mentioned above, the wearable display system 60 includes one or more optical elements having one or more grating structures that improve the optical performance of the wearable display system. For example, referring to Figures 7A and 7B, a diffractive relief structure, a grating 710, 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 illustrated 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 grating 710 diffracts incident guided light such that at least a portion of the light is extracted from the light guide 710 toward a user of the display system.

[0068] With specific reference to FIG. 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 through the EPE by the user, the light diffracted from the world may appear as undesirable image artifacts. The angle of incidence that creates the artifacts in the user's field of view generally depends on the design on the display combiner. For diffractive waveguide-based display combiners, large angles of incidence often result in stray light paths closest to the center of the user's world view.

[0069] This effect is further illustrated in FIG. 8A, which shows a display combiner 800. Ambient light is incident at an angle of incidence θ inc , 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. However, the display combiner 800 supports a grating (not shown) that diffracts at least a portion of the incident light towards the user. This light, labeled stray light, is incident on the front surface of the display combiner 800 at an angle θ stray It diffracts at

[0070] 8B, an angularly selectable film 810 can be applied to (e.g., laminated onto) the display combiner 800 to reduce stray light artifacts associated with ambient light. In general, the transmittance of light through the film 810 depends on the angle of incidence of the light on the film. As shown, the film 810 is configured to provide a relatively high (e.g., 30° or greater, 35° or greater, 40° or greater, 45° or greater, such as a user might experience from overhead lighting in an indoor environment) incidence angle θ inc , which reduces (e.g., blocks) the transmission of light but at a lower incidence angle θ a The angularly-selectable film transmits light (e.g., "world light" as seen by the wearer within the core field of view of the device) having a wavelength of 0.1 nm to 0.5 nm. 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 transmission efficiency for incident light generally varies as a function of the angle of incidence from relatively high transmission efficiencies (e.g., 40% or more, 45% or more) to relatively low transmission efficiencies (e.g., less than 1%, less than 0.5%). Transmission efficiency refers to the relative intensity of light transmitted at a particular wavelength. In some embodiments, unpolarized light with a wavelength in the range of 420 nm to 680 nm incident on the angularly-selectable film with an angle of incidence of 35° to 65° has a transmission efficiency of less than 0.5%. In some embodiments, unpolarized light with a wavelength in the range of 420 nm to 680 nm incident on the angularly-selectable film with an angle of incidence of -32° to +32° has a transmission efficiency of greater than 45%.

[0072] The angularly selectable film may also only affect the color of an image viewed through the film relatively little. For example, for a D65 source, the angularly selectable film may shift the CIE 1931 white point by less than (+ / -0.02, + / -0.02) (e.g., (+ / -0.01, + / -0.01) or less) for unpolarized light with angles of incidence between -32° and +32° for a (0.33, 0.33) CIE 1931 white point.

[0073] The transmittance of an angularly-selectable film can also be characterized by attenuation, which can be high at relatively high angles of incidence (e.g., 10 dB or more, 15 dB or more, 20 dB or more, 25 dB or more, 30 dB or more). Light at lower angles of incidence, such as 25° or less (e.g., 20° or less, 15° or less, 10° or less), can experience very low levels of attenuation (e.g., 2 dB or less, 1 dB or less).

[0074] In general, the angularly selectable film 810 can be relatively thin. For example, the film 810 can have a total thickness in the range of 500 microns to 2,000 microns. Thus, the advantages of using an angularly selectable film 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 that includes a polarization-adjusting film arranged between a pair of polarizer films (e.g., linear polarizers). The polarizer and polarization-adjusting films significantly reduce the transmission of visible light incident on the angularly-selectable film 810 at large angles of incidence without significantly reducing the transmission of light incident on the angularly-selectable film at small angles of incidence.

[0076] In general, the configuration of the two polarizers and the polarization adjustment film can be varied to provide a desired level of transmission variation over the angular incidence range of interest (e.g., −75° to +75°). In some embodiments, the polarizers are linear polarizers and the pass axes of the two linear polarizers can be crossed (e.g., at 90°).

[0077] In general, 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 can include A-plates (e.g., quarter-wave plates (QW)), in which the extraordinary axis of the birefringent material is parallel to the plane of the layer, and / or C-plates, in which the extraordinary axis of the birefringent material is perpendicular to the plane of the layer, with exemplary arrangements shown below. More generally, the birefringent layers can include uniaxial (e.g., as an A-plate or C-plate) or biaxial birefringent materials.

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

[0079] Generally, the angularly selectable film is appropriately sized to cover at least a portion of the eyepiece of the wearable display system. For example, in some embodiments, the angularly selectable film can have an area greater than 50 mm by 50 mm.

[0080] Turning now to a specific example of an angularly selectable film, and referring to Figure 9, an eyepiece 900 of a wearable display system includes a display combiner 800 and a film stack 910, which operates as the 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 either side of a C-plate 940.

[0081] The fast axes of waveplates 930a and 930b are oriented at approximately 45° to the pass 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 to approximately 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 handedness of each circular polarizer is identical.

[0082] C-plate 940 has zero phase difference for normally incident light, but a non-zero phase difference for obliquely incident light. Without wishing to be bound by theory, the retardation of a C-plate as a function of incidence angle is: [ka] where n0 is the ordinary refractive index of the C-plate and n e is the extraordinary refractive index of the C-plate, θ is the angle of incidence relative to the normal to the C-plate interface, k0=2π / λ is the wavenumber of the incident light, λ is the wavelength of the incident light, and d is the thickness of the C-plate. By using circularly polarized light, the excitation of ordinary and extraordinary modes in the C-plate for all angles of incidence is approximately equal. This can be seen from the input circular polarization state as T=cos 2 This leads to a transmission of (Γ / 2) to the same circular polarization state at the output.

[0083] An example of the transmission as a function of incidence angle for stack 910 is shown in FIG. 10, where the transmission as a function of incidence angle is n o =1.5236, n e = 1.52, and d = 153 μm. The transmission is here normalized to 1 for on-axis light, remains at or close to 1 up to about 20°, and then drops monotonically to zero at 60° to 80°, depending on the wavelength. For shorter wavelengths (e.g., 460 nm to 525 nm), the transmission increases as the angle of incidence increases up to 90°.

[0084] FIG. 9 shows an example of an angularly selectable film including a birefringent layer between two linear polarizers, although implementations with additional layers are also possible. For example, FIG. 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. A first polarization adjustment stack is arranged between polarizers 1020a and 1020b. The stack includes a pair of QWs 1030a and 1030b on either side of a C-plate 1040a. A second polarization adjustment stack is arranged between polarizers 1020b and 1020c. The stack includes QWs 1030c and 1030d on either side of a C-plate 1040b. In effect, the stack 1010 performs like two stacks 910 stacked together.

[0085] Stack 910 may be considered a single stage arrangement, and stack 1010 may be considered a dual stage. In general, additional stages may be added. Without wishing to be bound by theory, it is believed that several stages may be used in series to provide different transmittance responses. [ka] and Γ n is the delay of the nth stage.

[0086] The serial use of multiple stages can enable stronger attenuation of light from large angles of incidence. For example, referring to FIG. 11, the transmittance as a function of angle of incidence for a two-stage C-plate arrangement such as stack 1010 is shown. In this example, no=1.5236, ne=1.52, the thickness of the C-plate in the first stage (i.e., 1040b) is d1=111 μm, and the thickness of the C-plate in the second stage (i.e., 1040a) is d2=111 μm. Compared to the single stage film depicted in FIG. 10, the transmittance at high angles of incidence up to 90° remains low from 460 nm to 525 nm, rather than increasing from a minimum of 60° to 80°.

[0087] A variety of suitable different materials can be used for each layer in the angularly selectable film. The linear polarizer can be formed, for example, from a stretched polymer material (e.g., PVA) that is dyed 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. The QWs can be made, for example, from stretched polymer films or liquid crystal polymer films. The C-plate can be formed, for example, from a cast polymer film, such as cast cellulose triacetate. A liquid crystal polymer C-plate is also a possibility.

[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 with different optical properties than its neighbors. Similarly, multi-layer QWs can also be used.

[0089] In general, the film stack can include additional layers other than those described above. For example, the stack can include additional layers to provide a mechanical function rather than an optical function. Adhesive layers and / or layers for mechanical strength and / or environmental protection can be included. Such layers can be optically isotropic so as not to significantly affect the polarization of the transmitted light. In some embodiments, the stack includes one or more layers on the world side of the outermost linear polarizer. For example, anti-reflective films and / or hard coat layers can be included.

[0090] While the above-mentioned examples of angularly selectable films include optically passive elements, more generally, implementations can also feature optically active elements. Such elements can change their optical properties, and thus the transmissive properties, of the angularly selectable films in response to an electrical signal or some other physical stimulus. For example, FIG. 13 shows an eyepiece 1100 that includes a stack 1110 on a display combiner 800 that includes several passive optical films as well as a liquid crystal (LC) segmented 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. Effectively, the stack 1110 corresponds to a single stage attenuator (as shown in FIG. 9) stacked with an LC dimmer 1150 .

[0091] The segmented LC dimmer 1150 is a pixelated device that allows variable control of light transmission 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 can be patterned to form pixels, each of which can be individually addressed by a drive signal to control the orientation of the LC molecules in the LC layer. The transmission 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, e.g., the transmission through the dimmer is constant across its area but varies over time. For example, the transmission through the dimmer can be reduced in bright ambient environments, e.g., when the system is used in direct sunlight. In darker environments, the transmission can be increased.

[0092] The LC dimmer 1150 can also vary the transmission through the stack across the area of ​​the eyepiece. For example, in an area with substantial overhead lighting, the LC dimmer 1150 can reduce the transmission in the upper half of the eyepiece while leaving the transmission in the lower half of the eyepiece relatively high.

[0093] Using spatial control of an LC dimmer over 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 can be darkened in front of the eyepiece area, which creates stray light paths, thus reducing the magnitude of associated artifacts.

[0094] Dimmers can also be included in multi-stage stacks. For example, referring to FIG. 14, eyepiece 1200 includes stack 1210 mounted on display combiner 800, which includes two stages of angularly selectable film plus segmented dimmer 1250. Specifically, stack 1210 includes polarizers 1220a, 1220b, 1220c, and 1220d. Dimmer 1250 is located between polarizers 1220a and 1220b, closest to display combiner 800. One stage of angularly selectable film includes QWs 1230a and 1230b arranged on either side of C-plate 1240a. The other stage includes QWs 1230c and 1230d arranged on either side of C-plate 1240b.

[0095] In some embodiments, a dimmer can be included between the stages of the angularly selectable film. For example, FIG. 15 shows an eyepiece 1300 including a stack 1310 on the world side of the display combiner 800, which includes 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 the polarizers 1320a and 1320b, closest to the display combiner 800. One stage of the angularly selectable film includes QWs 1330a and 1330b, which are arranged on either side of the C-plate 1340a. The other stage includes QWs 1330c and 1330d, which are arranged on either side of the C-plate 1340b.

[0096] Installing a single-stage angularly selectable film on both sides of the dimmer, as in FIG. 15, may be advantageous from a mechanical perspective to conserve space in a stack of optical components used in an augmented reality display, for example, rather than having a two-stage angularly selectable film on one side of the dimmer, as in FIG.

[0097] Some implementations described herein can be implemented as one or more groups or modules of digital electronic circuitry, computer software, firmware, or hardware, or in a combination of one or more of them. Although different modules can be used, each module need not be distinct, and multiple modules can be implemented on the same digital electronic circuitry, computer software, firmware, or hardware, or combinations thereof.

[0098] Some implementations described herein can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a computer storage medium for execution by or to control the operation of a data processing apparatus. The computer storage medium can be or be included in 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 them. Furthermore, a computer storage medium is not a propagating signal, but a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagating signal. A computer storage medium can also be or be included in one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

[0099] The term "data processing apparatus" encompasses all kinds of apparatus, devices, and machines for processing data, including, by way of example, a programmable processor, a computer, a system on a chip, or a plurality or combination of the above. The apparatus may include special purpose logic circuitry, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). In addition to hardware, the apparatus may also include code that creates an execution environment for the computer program, such as code that constitutes a processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of these. The apparatus and execution environment may implement a variety of different computing model infrastructures, such as web services, distributed computing, and grid computing infrastructures.

[0100] A computer program (also known as a program, software, software application, script, 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 need not, correspond to a file in a file system. A program can be stored within a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), within a single file dedicated to the program, or within multiple cooperating files (e.g., files that store one or more modules, subprograms, or portions of code). A computer program can be deployed to run on one computer or on multiple computers located at one 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 operating on input data and generating output. The processes and logic flows can also be implemented by special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit), and an apparatus can also be implemented as such.

[0102] Processors suitable for executing computer programs include, by way of 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 a read-only memory or a random access memory or both. A computer includes a processor for performing actions according to the instructions and one or more memory devices for storing instructions and data. A computer may also include one or more mass storage devices, such as magnetic, magneto-optical, or optical disks, for storing data, or be operatively coupled thereto for receiving data therefrom, transferring data thereto, or both. However, a computer need not have such devices. Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, by way of 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. The processor and memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0103] To provide for interaction with a user, the operations 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) by which the user may provide input to the computer. Other types of devices can be used to provide interaction with the user as well, e.g., feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback, and input from the user can be received in any form, including acoustic, speech, or tactile input. Additionally, the computer can interact with the user by sending documents to and receiving documents from a device used by the user, e.g., by sending a web page to a web browser on the user's client device in response to a request received from the web browser.

[0104] A computer system may include a single computing device or multiple computers operating in close proximity to each other or generally remotely and typically interacting through a communications network. Examples of communications networks include local area networks ("LANs") and wide area networks ("WANs"), networks between networks (e.g., the Internet), networks with satellite links, and peer-to-peer networks (e.g., ad hoc peer-to-peer networks). The relationship of client and server may arise by virtue of computer programs running on separate computers and having a client-server relationship to each other.

[0105] 16 illustrates an exemplary computer system 1600 including a processor 1610, a memory 1620, a storage device 1630, and an input / output device 1640. Each of the components 1610, 1620, 1630, and 1640 can be interconnected, for example, by a system bus 1650. The processor 1610 can process 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 can process instructions stored in the memory 1620 or on the storage device 1630. The memory 1620 and the storage device 1630 can store information within the system 1600.

[0106] The input / output devices 1640 provide input / output operations for the system 1600. In some implementations, the input / output devices 1640 can include one or more of 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 devices can include a driver device configured to receive input data and send 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 can also be used.

[0107] Although the specification contains many details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features that are described in the specification in the context of separate implementations can also be combined. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple embodiments separately or in any suitable subcombination.

[0108] Several implementations have been described. However, it is to be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.

Claims

1. A wearable display system, comprising: an eyepiece stack that transmits ambient light from a world side to a user side opposite the world side, and during use, a user positioned on the user side views through the eyepiece stack a displayed image delivered by the wearable display system that extends the user's field of view; an angularly selectable film arranged on a world side of the eyepiece stack, the angularly selectable film comprising a passive polarization adjusting film arranged between a pair of linear polarizers; Equipped with the linear polarizer and polarization adjusting film significantly reduce the transmission of visible light incident on the angularly selectable film at large angles of incidence without significantly reducing the transmission of light incident on the angularly selectable film at small angles of incidence; A wearable display system, wherein for a D65 source, the angularly selectable film shifts the CIE 1931 white point by less than (+ / -0.02, + / -0.02) for unpolarized light with angles of incidence from -32° to +32° (0.33, 0.33).

2. A wearable display system, comprising: an eyepiece stack having a world side and a user side opposite the world side, wherein during use, a user positioned on the user side views through the eyepiece stack displayed images delivered by the wearable display system that extend the user's field of view; an angularly selectable film arranged on a world side of the eyepiece stack, the angularly selectable film comprising a passive polarization adjusting film arranged between a pair of linear polarizers; Equipped with the linear polarizer and polarization adjusting film significantly reduce the transmission of visible light incident on the angularly selectable film at large angles of incidence without significantly reducing the transmission of light incident on the angularly selectable film at small angles of incidence; A wearable display system, wherein for a D65 source, the angularly selectable film shifts the CIE 1931 white point by less than (+ / -0.02, + / -0.02) for unpolarized light with angles of incidence from -32° to +32° (0.33, 0.33).

3. The wearable display system of claim 2 , wherein the pass axes of the two linear polarizers are crossed.

4. The wearable display system of claim 2 , wherein the polarization adjusting film rotates the polarization state of light transmitted by a first linear polarizer of the pair of linear polarizers on a world-side of the polarization adjusting film.

5. The wearable display system of claim 4 , wherein the amount of rotation of the polarization state varies depending on the angle of incidence of light transmitted by a first linear polarizer of the pair of linear polarizers.

6. The wearable display system of claim 5 , wherein the light transmitted with a large angle of incidence is rotated less than the light transmitted with a small angle of incidence.

7. 3. The wearable display system of claim 2, wherein unpolarized light with a wavelength in the range of 420 nm to 680 nm incident on the angularly selectable film with an incidence angle of 35° to 65° has a transmittance efficiency of less than 0.5%.

8. The wearable display system of claim 2 , wherein the angularly selectable film has an area greater than 50 mm by 50 mm.

9. The wearable display system of claim 2 , wherein the polarization adjusting film comprises at least one layer of birefringent material.

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

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

12. The wearable display system of claim 11, wherein each quarter-wave plate is aligned with a corresponding one of the linear polarizers to form a circular polarizer.

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

14. 3. The wearable display system of claim 2, 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 of claim 14 , wherein the first and second polarization adjusting films each consist of one or more layers of birefringent material.

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

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

18. 3. The wearable display system of claim 2, wherein the angularly selectable film comprises two or more stages, each stage comprising a polarization adjusting film arranged between a pair of linear polarizers.

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

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