Afterimage reduction in see-through displays with pixel arrays

Abstract

To provide a ghost image mitigation in a see-through display with a pixel array.SOLUTION: A head-mounted apparatus includes an eyepiece that includes a variable dimming assembly and a frame mounting the eyepiece so that a user side of the eyepiece faces toward a user and a world side of the eyepiece opposite to the first side faces away from the user. A dynamic dimming assembly selectively modulates the intensity of light transmitted parallel to an optical axis from the world side to the user side during operation. The dynamic dimming assembly includes a variable birefringence cell having a plurality of pixels each having an independently variable birefringence, a first linear polarizer arranged on the user side of the variable birefringence cell, the first linear polarizer being configured to transmit light propagating parallel to the optical axis linearly polarized along a pass axis of the first linear polarizer orthogonal to the optical axis, and a 1 / 4 wavelength plate arranged between the variable birefringence cell and the first linear polarizer.SELECTED DRAWING: Figure 7A

Description

Technical Field

[0001] (Cross - reference to Related Applications) This application claims the priority of Provisional Application No. 62 / 887,639, filed on August 15, 2019, entitled "GHOST IMAGE MITIGATION IN SEE - THROUGH DISPLAYS WITH PIXEL ARRAYS", the entire content of which is incorporated herein by reference.

Background Art

[0002] Modern computing and display technologies have facilitated the development of systems for so - called "virtual reality" or "augmented reality" experiences, where digitally reproduced images or portions thereof are presented to a user in a manner that appears or is perceived to be real. Virtual reality, i.e., "VR" scenarios, typically involve the presentation of digital or virtual image information without transparency to other actual real - world visual inputs. Augmented reality, i.e., "AR" scenarios, typically involve the presentation of digital or virtual image information as an augmentation to the visualization of the actual world around the user.

[0003] Despite the progress made in these display technologies, there remains a need in the art for improved methods, systems, and devices related to augmented reality systems, particularly display systems.

Summary of the Invention

Means for Solving the Problems

[0004] Segmented attenuation using polarized TFT-LCD panels can significantly increase the visibility and realism of content without dimming the entire field of view of the world. Display light in a diffraction waveguide type see-through AR display transmits light in two directions: one towards the user and one towards the world. Back reflections of light traveling towards the world (e.g., from metal traces, conductors, layer refractive index mismatches, and reflective components of dimming assemblies such as TFTs) can appear as "afterimage" images next to the primary display image. These afterimage images affect the effective contrast and visual fidelity of virtual content, and therefore the quality of immersion. Mitigating afterimages and stray light paths caused by metal traces, TFTs, layer refractive index mismatches, elements / objects beyond the dimmer, etc., is a challenging problem.

[0005] The systems and techniques disclosed herein utilize the polarizing film of a dimmer as both a system optical isolator and an internal optical isolator of the dimmer, thereby effectively suppressing such "afterimage" images. The addition of a refractive index matching fluid / gel between the eyepiece cover glass and the dimmer, whose refractive index is close to that of the first layer of the dimmer, can reduce afterimages from the first dimmer surface.

[0006] The use of a specificly selected achromatic quarter-wave plate (QWP) allows liquid crystal dimmers, such as those using electrically controlled birefringent (ECB) cells, to exhibit less polarization leakage, better color performance, and greater color neutrality across a relatively wide range of operating conditions.

[0007] This disclosure relates, in general terms, to techniques for improving optical systems when ambient light conditions are varied. More specifically, embodiments of this disclosure provide systems and methods for operating augmented reality (AR) devices that include dimming elements. While the invention is described with reference to AR devices, this disclosure is applicable to a variety of applications in computer vision and image display systems.

[0008] In general, in a first aspect, the present invention features a head-mounted device including an eyepiece, which includes a variable dimming assembly and a frame for mounting the eyepiece such that, during use of the head-mounted device, the user side of the eyepiece faces the user of the head-mounted device, and the world side of the eyepiece opposite the first side faces outward from the user. The dynamic dimming assembly is configured to selectively modulate the intensity of light transmitted from the world side of the eyepiece to the user side of the eyepiece parallel to the optical axis during operation of the head-mounted device. The dynamic dimming assembly includes a variable birefringence cell having a plurality of pixels, each independently having variable birefringence; a first linear polarizer arranged on the user side of the variable birefringence cell, configured to transmit light propagating parallel to the optical axis, which is linearly polarized along the passing axis of the first linear polarizer that is perpendicular to the optical axis; a quarter-wave plate arranged between the variable birefringence cell and the first linear polarizer, the fast axis of the quarter-wave plate being aligned with the passing axis of the first linear polarizer, and converting linearly polarized light transmitted by the first linear polarizer into circularly polarized light; and a second linear polarizer on the world side of the variable birefringence cell.

[0009] The implementation of a head-mounted device may include one or more of the following features and / or other features: For example, a dynamic dimming assembly may further include an optical retarder arranged between a variable birefringence cell and a second linear polarizer. The optical retarder may be a second quarter-wave plate. The optical retarder is an A-plate with a delay greater than that of the quarter-wave plate. The difference between the delay of the optical retarder and the delay of the quarter-wave plate may correspond to the residual delay of the variable birefringence cell in the minimum birefringence state.

[0010] A variable birefringence cell may include a layer of liquid crystal. The liquid crystal can be configured in electrically controllable birefringence modes. In some embodiments, the liquid crystal layer is a vertically aligned liquid crystal layer. The liquid crystal can be a nematic phase liquid crystal.

[0011] Pixels in a variable birefringence cell can be actively addressable pixels.

[0012] The eyepiece may further include a see-through display mounted within a frame on the user side of the variable dimming assembly. The see-through display may include one or more waveguide layers arranged to receive light from an optical projector and direct the light towards the user during the operation of the head-mounted device. The head-mounted device may include one or more refractive index matching layers arranged between the see-through display and the variable dimming assembly.

[0013] In some embodiments, the dynamic dimming assembly includes one or more anti-reflective layers.

[0014] In another aspect, the present invention features an augmented reality system including a head-mounted device.

[0015] In general, in another aspect, the present invention features a head-mounted device including an eyepiece, having a variable dimming assembly and a frame for mounting the eyepiece such that, during use of the head-mounted device, the user side of the eyepiece faces the user of the head-mounted device, and the world side of the eyepiece facing the first side faces outward from the user. The dynamic dimming assembly is configured to selectively modulate the intensity of light transmitted from the world side of the eyepiece to the user side of the eyepiece parallel to the optical axis during operation of the head-mounted device. The dynamic dimming assembly includes a layer of liquid crystal, a circular polarizer arranged on the user side of the liquid crystal layer, and a linear polarizer on the world side of the liquid crystal layer.

[0016] Embodiments of head-mounted devices may include one or more of the following features and / or other features: For example, a circular polarizer may include a linear polarizer and a quarter-wave plate. The head-mounted device may include an A-plate arranged between the linear polarizers on the world side of the liquid crystal layer.

[0017] The head-mounted device may include pixelated cells, which include a liquid crystal layer, and the pixelated cells are actively addressable pixelated cells.

[0018] In general, in further aspects, the present invention is characterized by a method for operating an optical system. The method may include the step of receiving light associated with a world object in the optical system. The method may also include the step of projecting a virtual image onto an eyepiece. The method may further include the step of determining a portion of the system field of view of the optical system that should be at least partially dimmed based on detected information. The method may further include the step of adjusting a dimmer to reduce the intensity of light associated with a world object in a portion of the system field of view.

[0019] In some embodiments, the optical system includes an optical sensor configured to detect optical information corresponding to light associated with a world object. In some embodiments, the detected information includes optical information. In some embodiments, the optical information includes a plurality of spatially resolved optical values. In some embodiments, the optical information includes a global optical value. In some embodiments, the optical system includes an eye tracker configured to detect line-of-sight information corresponding to the eye of the user of the optical system. In some embodiments, the detected information includes line-of-sight information. In some embodiments, the line-of-sight information includes pixel locations that intersect with the line-of-sight vector of the user's eye. In some embodiments, the line-of-sight information includes one or more of the user's eye pupil position, the user's eye rotation center, the user's eye pupil size, the user's eye pupil diameter, and the user's eye cone and rod locations. In some embodiments, the method further includes the step of detecting image information corresponding to a virtual image. In some embodiments, the detected information includes image information. In some embodiments, the image information includes a plurality of spatially resolved image brightness values. In some embodiments, the image information includes a global image brightness value.

[0020] In some embodiments, the method further includes the step of determining a plurality of spatially resolved dimming values ​​for a portion of the system field of view based on detected information. In some embodiments, the dimmer is adjusted according to the plurality of dimming values. In some embodiments, the dimmer comprises a plurality of pixels. In some embodiments, the dimmer is adjusted to completely block out the light intensity associated with world objects within the entire system field of view. In some embodiments, the method further includes the step of adjusting the brightness associated with a virtual image. In some embodiments, the virtual image is characterized by an image field of view. In some embodiments, the image field of view is equal to the system field of view. In some embodiments, the image field of view is a subset of the system field of view.

[0021] In general, in another aspect, the present invention features an optical system. The optical system may include a projector configured to project a virtual image onto an eyepiece. The optical system may also include a dimmer configured to dim the light associated with world objects. The optical system may further include a processor communicatively coupled to the projector and the dimmer. In some embodiments, the processor is configured to perform an operation that includes determining, based on detected information, a portion of the system field of view of the optical system to be at least partially dimmed. In some embodiments, the operation may also include adjusting the dimmer to reduce the intensity of the light associated with world objects within the portion of the system field of view.

[0022] In some embodiments, the optical system further includes an optical sensor configured to detect optical information corresponding to light associated with a world object. In some embodiments, the detected information includes optical information. In some embodiments, the optical information includes a plurality of spatially resolved optical values. In some embodiments, the optical information includes a global optical value. In some embodiments, the optical system further includes an eye tracker configured to detect line-of-sight information corresponding to the eyes of the user of the optical system. In some embodiments, the detected information includes line-of-sight information. In some embodiments, the line-of-sight information includes pixel locations that intersect with the line-of-sight vector of the user's eye. In some embodiments, the line-of-sight information includes one or more of the pupil position of the user's eye, the rotation center of the user's eye, the pupil size of the user's eye, the pupil diameter of the user's eye, and the cone and rod locations of the user's eye. In some embodiments, the operation further includes the step of detecting image information corresponding to a virtual image. In some embodiments, the detected information includes image information. In some embodiments, the image information includes a plurality of spatially resolved image brightness values. In some embodiments, the image information includes a global image brightness value.

[0023] In some embodiments, the operation further includes the step of determining a plurality of spatially resolved dimming values ​​for a portion of the system field of view based on detected information. In some embodiments, the dimmer is adjusted according to the plurality of dimming values. In some embodiments, the dimmer comprises a plurality of pixels. In some embodiments, the dimmer is adjusted to completely block out the light intensity associated with world objects within the entire system field of view. In some embodiments, the operation further includes the step of adjusting the brightness associated with a virtual image. In some embodiments, the virtual image is characterized by an image field of view. In some embodiments, the image field of view is equal to the system field of view. In some embodiments, the image field of view is a subset of the system field of view.

[0024] A number of advantages can be achieved by the method of the present disclosure that is superior to conventional techniques. For example, the AR device described herein may be used at light levels that vary from dark indoors to bright outdoors by globally dimming and / or selectively dimming the ambient light reaching the user's eyes. Embodiments of the present invention use a pixelated dimming device to enable AR and virtual reality (VR) capabilities within a single device by attenuating world light by more than 99%. Embodiments of the present invention also use discrete or continuously variable depth plane switching techniques to use variable focus elements to reduce the vergence / accommodation conflict. Embodiments of the present invention improve the battery life of an AR device by optimizing the projector brightness based on the amount of detected ambient light. Other advantages will also be readily apparent to those skilled in the art. The present invention provides, for example, the following. (Item 1) A head-mounted device, An eyepiece lens including a variable dimming assembly, A frame, wherein the frame mounts the eyepiece lens such that, during use of the head-mounted device, the user side of the eyepiece lens faces the user of the head-mounted device and the world side of the eyepiece lens facing the first side faces outward from the user. Comprising, The dynamic dimming assembly is configured to selectively modulate the intensity of light transmitted parallel to the optical axis from the world side of the eyepiece lens to the user side of the eyepiece lens during operation of the head-mounted device, and the dynamic dimming assembly A variable birefringence cell including a plurality of pixels each having independently variable birefringence, A first linear polarizer arranged on the user side of the variable birefringence cell, the first linear polarizer being configured to transmit light propagating parallel to the optical axis linearly polarized along the transmission axis of the first linear polarizer orthogonal to the optical axis. A quarter-wave plate arranged between the variable birefringence cell and the first linear polarizer, wherein the fast axis of the quarter-wave plate is arranged with respect to the transmission axis of the first linear polarizer, and the quarter-wave plate converts linearly polarized light transmitted by the first linear polarizer into circularly polarized light. A second linear polarizer on the world side of the variable birefringence cell A head-mounted device comprising the above. (Item 2) The head-mounted device according to item 1, wherein the dynamic dimming assembly further comprises an optical retarder arranged between the variable birefringence cell and the second linear polarizer. (Item 3) The head-mounted device according to item 2, wherein the optical retarder is a second quarter-wave plate. (Item 4) The head-mounted device according to item 2, wherein the optical retarder is an A-plate with a retardation exceeding that of the quarter-wave plate. (Item 5) The head-mounted device according to item 2, wherein the difference between the retardation of the optical retarder and the retardation of the quarter-wave plate corresponds to the residual retardation of the variable birefringence cell in the minimum birefringence state. (Item 6) The head-mounted device according to item 1, wherein the variable birefringence cell comprises a layer of liquid crystal. ​​​​​​​​​​​​​​​​​​The head-mounted device according to item 1, further comprising a see-through display mounted within a frame on the user side of the variable dimming assembly, wherein the eyepiece is further equipped with a see-through display. (Item 12) The head-mounted device according to item 11, wherein the see-through display comprises one or more waveguide layers arranged to receive light from an optical projector and direct the light toward the user during the operation of the head-mounted device. (Item 13) The head-mounted device according to item 12, further comprising one or more refractive index matching layers arranged between the see-through display and the variable dimming assembly. (Item 14) The head-mounted device according to item 1, wherein the dynamic dimming assembly comprises one or more anti-reflective layers. (Item 15) An augmented reality system equipped with the head-mounted device described in item 1. (Item 16) A head-mounted device, An eyepiece equipped with a variable dimming assembly, A frame, the frame is configured such that, during use of the head-mounted device, the user-side of the eyepiece faces the user of the head-mounted device, and the world-side of the eyepiece facing the first side faces outward from the user. Equipped with, The dynamic dimming assembly is configured to selectively modulate the intensity of light transmitted from the world side of the eyepiece to the user side of the eyepiece parallel to the optical axis during the operation of the head-mounted device, and the dynamic dimming assembly is configured to selectively modulate the intensity of light transmitted from the world side of the eyepiece to the user side of the eyepiece parallel to the optical axis, The liquid crystal layer, A circular polarizer arranged on the user side of the liquid crystal layer, A linear polarizer on the world side of the liquid crystal layer and A head-mounted device equipped with the following features. (Item 17) The circular polarizer is a head-mounted device according to item 16, comprising a linear polarizer and a quarter-wave plate. (Item 18) The head-mounted device according to item 17, further comprising A-plates arranged between linear polarizers on the world side of the liquid crystal layer. (Item 19) The head-mounted device according to item 16, comprising a pixelated cell having the liquid crystal layer, wherein the pixelated cell is an actively addressable pixelated cell. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 illustrates an augmented reality (AR) scene as viewed through a wearable AR device, according to some embodiments described herein.

[0026] [Figure 2A] Figure 2A illustrates one or more general features of an AR device according to the present invention.

[0027] [Figure 2B] Figure 2B illustrates an embodiment of an AR device in which the area to be dimmed is determined based on detected light information.

[0028] [Figure 2C] Figure 2C illustrates an embodiment of an AR device in which the area to be dimmed is determined based on a virtual image.

[0029] [Figure 2D] Figure 2D illustrates an embodiment of an AR device in which the area to be dimmed is determined based on line-of-sight information.

[0030] [Figure 3] Figure 3 illustrates a schematic diagram of a wearable AR device according to the present invention.

[0031] [Figure 4] Figure 4 illustrates the method for operating the optical system.

[0032] [Figure 5] Figure 5 illustrates an AR device with an eyepiece and a pixelated light-adjusting element.

[0033] [Figure 6A] Figure 6A is a front view of an exemplary optically transparent spatial light modulator ("SLM") or display assembly for a see-through display system, according to some embodiments of the present disclosure.

[0034] [Figure 6B] Figure 6B is a schematic side view of the exemplary SLM or display assembly shown in Figure 6A.

[0035] [Figure 7A] Figure 7A illustrates an embodiment of the see-through display system in the first state.

[0036] [Figure 7B] Figure 7B illustrates an embodiment of the see-through display system shown in Figure 7A in a second state, which is different from the first state.

[0037] [Figure 8A] Figure 8A illustrates another embodiment of a see-through display system in the first state.

[0038] [Figure 8B] Figure 8B illustrates an embodiment of the see-through display system shown in Figure 8A in a second state, which is different from the first state.

[0039] [Figure 9] Figure 9 illustrates an embodiment of a see-through display system according to several embodiments of the present disclosure.

[0040] [Figure 10] Figure 10 illustrates an embodiment of a see-through display system according to another embodiment of the present disclosure.

[0041] [Figure 11] Figure 11 illustrates an embodiment of a see-through display system according to yet another embodiment of the present disclosure.

[0042] [Figure 12] Figure 12 is a schematic diagram of an exemplary computer system useful with a see-through display system. [Modes for carrying out the invention]

[0043] Detailed explanation An ongoing technical challenge with optical see-through (OST) augmented reality (AR) devices is the variation in opacity and / or visibility of virtual content under fluctuating ambient light conditions. The problem worsens in extreme lighting conditions, such as in a completely dark room or outdoors in completely bright sunlight. Embodiments disclosed herein can mitigate (e.g., solve) these and other problems by dimming the world light at different spatial locations within the field of view of the AR device. In such a variable dimming array, the AR device can determine which parts of the field of view to dim and the amount of dimming to apply to each part, based on various information detected by the AR device. This information may include detected ambient light, detected line-of-sight information, and / or detected brightness of the projected virtual content. The functionality of the AR device can be further improved by detecting directions associated with ambient light, for example, by detecting multiple spatially resolved light intensity values. This can improve the battery life of the AR device by dimming only the parts of the field of view that require dimming and / or increasing the projector brightness within certain parts of the field of view. Therefore, the embodiments disclosed herein can enable the use of AR devices in a much wider range of ambient lighting conditions than is conventionally conceivable.

[0044] Figure 1 illustrates an AR scene as viewed through a wearable AR device, according to several embodiments described herein. An AR scene 100 is depicted in which a user of the AR technology can see a real-world park-like setting 106, featuring people, trees, buildings in the background, and a concrete platform 120. In addition to these items, the user of the AR technology also perceives "seeing" a robotic figure 110 standing on the real-world platform 120 and a flying cartoonish avatar character 102 that appears to be a personification of a bumblebee, although these elements (character 102 and figure 110) do not exist in the real world. Due to the significant complexity of human visual perception and the nervous system, producing virtual reality (VR) or AR technology that facilitates a comfortable, natural, and rich presentation of virtual image elements among other virtual or real-world image elements is challenging.

[0045] Figure 2A illustrates general features of one or more exemplary AR devices 200. The AR device 200 includes an eyepiece 202 and a dynamic dimmer 203, which are configured to be transparent or translucent when the AR device 200 is in an inactive or off mode, so that when viewed through the eyepiece 202 and the dynamic dimmer 203, the user can view one or more world objects 230. As illustrated, the eyepiece 202 and the dynamic dimmer 203 are arranged in a juxtaposed configuration and form a system field of view that is visible to the user when viewed through the eyepiece 202 and the dynamic dimmer 203. In some embodiments, the system field of view is defined as the entire two-dimensional region occupied by one or both of the eyepiece 202 and the dynamic dimmer 203. Figure 2A illustrates a single eyepiece 202 and a single dynamic dimmer 203 (for illustrative purposes), but generally, an AR device 200 includes two eyepieces and two dynamic dimmers for each of the user's eyes.

[0046] During operation, the dynamic dimmer 203 may be adjusted to vary the intensity of world light 232 transmitted from the world object 230 to the eyepiece 202 and the user, thereby providing a dimmed area 236 within the system field of view that transmits less world light than other areas of the dynamic dimmer 203. The dimmed area 236 may be part or a subset of the system field of view and may be partially or completely dimmed. A partially dimmed area will transmit a certain percentage of the incident world light, while a completely dimmed area will block substantially all of the incident world light. The dynamic dimmer 203 may be adjusted according to a plurality of spatially resolved dimming values ​​for the dimmed area 236.

[0047] Furthermore, during the operation of the AR device 200, the projector 214 may project a virtual image 222 onto the eyepiece 202, which can be observed by the user along with the world light 232. Projecting the virtual image 222 onto the eyepiece 202 projects a light field 223 (i.e., an angular representation of the virtual content) onto the user's retina, so that the user perceives the corresponding virtual content as being located in a place within the user's environment. Note that the virtual content (character 102 and image 110) is depicted in Figure 2A-2D as it appears on the eyepiece 202 for illustrative purposes only. The virtual content can actually be perceived by the user at various depths beyond the eyepiece 202. For example, the user may perceive the image 110 as being located at approximately the same distance as the world object 230 (i.e., platform 120), and the character 102 as being located closer to the user. In some embodiments, the dynamic dimmer 203 may be positioned closer to the user than the eyepiece 202, and therefore may reduce the intensity of light associated with the virtual image 222 (i.e., the light field 223). In some embodiments, two dynamic dimmers may be used, one on each side of the eyepiece 202.

[0048] As described, the AR device 200 includes an ambient light sensor 234 configured to detect world light 232. The ambient light sensor 234 may be positioned such that the world light 232 detected by the ambient light sensor 234 is similar to and / or represents the world light 232 that strikes the dynamic dimmer 203 and / or eyepiece 202. In some embodiments, the ambient light sensor 234 may be configured to detect multiple spatially resolved light values ​​corresponding to different pixels of the dynamic dimmer 203. In some embodiments, or identical embodiments, the ambient light sensor 234 may be configured to detect a global light value corresponding to the average or single light intensity of world light 232. Other possibilities are also considered.

[0049] Figure 2B illustrates the AR device 200 in a state where the dimmed area 236 is determined based on detected light information corresponding to world light 232. Specifically, the ambient light sensor 234, in this embodiment, detects world light 232 from the sun 233 and may further detect the direction and / or portion of the system field of view through which the world light 232 associated with the sun passes through the AR device 200. In response, the dynamic dimmer 203 sets the dimmed area 236 and adjusts to cover the portion of the system field of view corresponding to the detected world light, reducing the intensity of world light from the sun 233 to the eyepiece 202 and the user. As shown, the dynamic dimmer 203 adjusts to reduce the transmitted intensity of world light 232 at the center of the dimmed area 236 by an amount exceeding that at the edges of the dimmed area 236.

[0050] Figure 2C illustrates the AR device 200 in a state where the dimmed area 236 is determined based on the location of the virtual image 222 in the field of view. Specifically, the dimmed area 236 is determined based on the virtual content perceived by the user, resulting from the user observing the virtual image 222. In some embodiments, the AR device 200 may detect image information, among other possibilities, including the location of the virtual image 222 (e.g., the location in the system's field of view and / or the corresponding location of the dynamic dimmer 203 through which the user perceives the virtual content) and / or the brightness of the virtual image 222 (e.g., the brightness of the perceived virtual content). As shown, the dynamic dimmer 203 may set the dimmed area 236 and adjust it to cover the portion of the system's field of view corresponding to the virtual image 222, or alternatively, in some embodiments, the dimmed area 236 may cover a portion of the system's field of view that is not aligned with the virtual image 222. In some embodiments, the dimming value of the dimmed area 236 may be determined based on the brightness of the world light 232 and / or virtual image 222 detected by the ambient light sensor 234.

[0051] Figure 2D illustrates the AR device 200 in a state where the dimmed area 236 is determined based on gaze information corresponding to the user's eyes. In some embodiments, the gaze information includes the user's gaze vector 238 and / or the pixel locations of the dynamic dimmer 203 where the gaze vector 238 intersects with the dynamic dimmer 203. As shown, the dynamic dimmer 203 may set the dimmed area 236 and adjust to cover the portion of the system field of view corresponding to the intersection (or crossing region) between the gaze vector 238 and the dynamic dimmer 203, or alternatively, in some embodiments, the dimmed area 236 may cover the portion of the system field of view that does not correspond to the intersection (or crossing region) between the gaze vector 238 and the dynamic dimmer 203. In some embodiments, the dimming value of the dimmed area 236 may be determined based on the brightness of the world light 232 and / or virtual image 222 detected by the ambient light sensor 234. In some embodiments, the gaze information may be detected by an eye tracker 240 mounted on the AR device 200.

[0052] Figure 3 illustrates a schematic diagram of a further exemplary wearable AR device 300. The AR device 300 includes a left eyepiece 302A and a left dynamic dimmer 303A, arranged in a juxtaposed configuration, and a right eyepiece 302B and a right dynamic dimmer 303B, similarly arranged in a juxtaposed configuration. As described, the AR device 300 includes, but is not limited to, one or more sensors, including: a left-facing world camera 306A mounted directly on or near the left eyepiece 302A; a right-facing world camera 306B mounted directly on or near the right eyepiece 302B; a left-facing world camera 306C mounted directly on or near the left eyepiece 302A; a right-facing world camera 306D mounted directly on or near the right eyepiece 302B; a left eye tracker 340A positioned to observe the user's left eye; a right eye tracker 340B positioned to observe the user's right eye; and an ambient light sensor 334. The AR device 300 also includes one or more image projection devices, such as a left projector 314A optically linked to the left eyepiece 302A, and a right projector 314B optically linked to the right eyepiece 302B.

[0053] Some or all of the components of the AR device 300 may be head-mounted so that the projected image can be viewed by the user. In some implementations, all of the components of the AR device 300 shown in Figure 3 are mounted on a single device (e.g., a single headset) that can be worn by the user. In some implementations, the processing module 350 is physically separate and communicatively coupled to the other components of the AR device 300 by one or more wired and / or wireless connections. For example, the processing module 350 may be mounted in various configurations, such as being fixed to a frame, fixed to a helmet or hat worn by the user, built into headphones, or otherwise removable by the user (e.g., in a backpack configuration, in a belt-mounted configuration, etc.).

[0054] The processing module 350 may include a processor 352 and associated digital memory 356, such as non-volatile memory (e.g., flash memory), both of which may be used to assist in data processing, caching, and storage. The data may include data captured from sensors (e.g., operably coupled to the AR device 300 or otherwise attached to the user), such as a camera 306, an ambient light sensor 334, an eye tracker 340, a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope. For example, the processing module 350 may receive an image 320 from the camera 306. Specifically, the processing module 350 may receive a left front image 320A from a left-facing world camera 306A, a right front image 320B from a right-facing world camera 306B, a left-side image 320C from a left-facing world camera 306C, and a right-side image 320D from a right-facing world camera 306D. In some embodiments, the image 320 may include a single image, a pair of images, a video comprising a stream of images, a video comprising a paired stream of images, and equivalents. The image 320 may be generated periodically while the AR device 300 is powered on and transmitted to the processing module 350, or generated in response to a command transmitted by the processing module 350 to one or more of the cameras. In another embodiment, the processing module 350 may receive light information from the ambient light sensor 334. In another embodiment, the processing module 350 may receive gaze information from one or both of the eye trackers 340. In another embodiment, the processing module 350 may receive image information (e.g., image brightness values) from one or both of the projectors 314.

[0055] The eyepieces 302A and 302B each include a transparent or translucent waveguide configured to direct light from the projectors 314A and 314B, respectively. Specifically, the processing module 350 may cause the left projector 314A to output a left virtual image 322A onto the left eyepiece 302A (projecting a corresponding light field associated with the left virtual image 322A onto the user's retina), and the right projector 314B to output a right virtual image 322B onto the right eyepiece 302B (projecting a corresponding light field associated with the right virtual image 322B onto the user's retina). In some embodiments, each eyepiece 302 includes a plurality of waveguides corresponding to different colors and / or different depth planes. In some embodiments, a dynamic dimmer 303 may be coupled to and / or integrated with the eyepiece 302. For example, one of the dynamic dimmers 303 may be incorporated into a multilayer eyepiece, forming one or more layers that constitute one of the eyepieces 302.

[0056] Cameras 306A and 306B may be positioned to capture images that substantially overlap with the field of view of the user's left and right eyes, respectively. Thus, the placement of camera 306 may be close to the user's eyes, but not so close that it obscures the user's field of view. Alternatively, or in addition, cameras 306A and 306B may be positioned to align with the internal joining locations of virtual images 322A and 322B, respectively. Cameras 306C and 306D may be positioned to capture images to the side of the user, for example, within or outside the user's peripheral vision. Images 320C and 320D captured using cameras 306C and 306D do not necessarily have to overlap with images 320A and 320B captured using cameras 306A and 306B.

[0057] One or more components of the AR device 300 may be analogous to one or more components described with reference to Figures 2A-2D. For example, in some embodiments, the functionality of the eyepiece 302, dynamic dimmer 303, projector 314, ambient light sensor 334, and eye tracker 340 may be analogous to the eyepiece 202, dynamic dimmer 203, projector 214, ambient light sensor 234, and eye tracker 240, respectively. In some embodiments, the functionality of the processing module 350 may be implemented by two or more sets of electronic hardware components that are separately stored but communicatively coupled. For example, the functionality of the processing module 350 may be performed by electronic hardware components housed within the headset in conjunction with an electronic hardware component housed within the headset, one or more electronic devices in the headset's environment (e.g., a smartphone, computer, peripheral device, smart home appliance, etc.), one or more remotely located computing devices (e.g., a server, cloud computing device, etc.), or a combination thereof. One embodiment of such a configuration is described in more detail below with reference to Figure 12.

[0058] Figure 4 illustrates an exemplary method 400 for operating an optical system (e.g., AR device 200 or 300). In general, the operation of the optical system may include steps of performing the steps of method 400, as shown in Figure 4 or in a different order, and not all of the steps need to be performed. For example, in some embodiments, one or more of steps 406, 408, and 410 may be omitted during the implementation of method 400. One or more of the steps of method 400 may be performed by a processor (e.g., processor 352) or some other component in the optical system.

[0059] In step 402, light associated with an object (e.g., world object 230) (e.g., world light 232) is received in the optical system. The object may be a real-world object visible to a user of the optical system, such as a tree, a person, a house, a building, or the sun. In some embodiments, the light associated with the object is first received by a dynamic dimmer (e.g., dynamic dimmer 203 or 303) or an aesthetic lens outside the optical system. In some embodiments, the light associated with the object is considered received in the optical system when the light reaches one or more components of the optical system (e.g., when the light reaches a dynamic dimmer).

[0060] In step 404, a virtual image (e.g., virtual image 222 or 322) is projected onto the eyepiece (e.g., eyepiece 202 or 302). The virtual image may be projected onto the eyepiece by a projector of the optical system (e.g., projector 214 or 314). The virtual image may correspond to a single image, a pair of images, a video consisting of a stream of images, a video consisting of a paired stream of images, and equivalents. In some embodiments, the virtual image is considered projected onto the eyepiece when any light associated with the virtual image reaches the eyepiece. In some embodiments, projecting the virtual image onto the eyepiece causes a light field (i.e., an angular representation of the virtual content) to be projected onto the user's retina so that the user perceives the corresponding virtual content as being located in a place within the user's environment.

[0061] Between steps 406, 408, and 410, information may be detected by the optical system, for example, using one or more sensors in the optical system. In step 406, optical information corresponding to light associated with an object is detected. The optical information may be detected using an optical sensor mounted on the optical system (e.g., ambient light sensor 234 or 334). In some embodiments, the optical information includes a plurality of spatially resolved optical values. Each of the plurality of spatially resolved optical values ​​may correspond to a two-dimensional position within the system's field of view. For example, each optical value may be associated with a pixel of a dynamic dimmer. In other embodiments, or in the same embodiments, the optical information may include a global optical value. The global optical value may be associated with the entire system's field of view (e.g., the average optical value of light that strikes all pixels of the dynamic dimmer).

[0062] In step 408, gaze information corresponding to the user's eye in the optical system is detected. The gaze information may be detected using an eye tracker (e.g., eye tracker 240 or 340) mounted on the optical system. In some embodiments, the gaze information includes the user's eye's gaze vector (e.g., gaze vector 238). In some embodiments, the gaze information includes one or more of the user's eye's pupil position, center of rotation, pupil size, pupil diameter, and cone and rod locations. The gaze vector may be determined based on one or more components of the gaze information, such as pupil position, center of rotation, pupil size, pupil diameter, and / or cone and rod locations. When the gaze vector is determined based on cone and rod locations, it may further be determined based on optical information (e.g., global optical values) to determine the origin of the gaze vector in the retinal layer of the eye, including the cone and rod locations. In some embodiments, the line-of-sight information includes pixels or groups of pixels of a dynamic dimmer where the line-of-sight vector intersects with the dynamic dimmer.

[0063] In step 410, image information corresponding to a virtual image (e.g., virtual image 222 or 322) projected onto the eyepiece by the projector is detected. The image information may be detected by the projector, by a processor (e.g., processor 352), or by a separate light sensor. In some embodiments, the image information includes one or more locations in the dynamic dimmer through which the user perceives virtual content when the user observes the virtual image. In some embodiments, the image information includes a plurality of spatially resolved image brightness values ​​(e.g., brightness of perceived virtual content). For example, each image brightness value may be associated with a pixel in the eyepiece or dynamic dimmer. In one particular implementation, when the processor sends an instruction to the projector and projects a virtual image onto the eyepiece, the processor may determine spatially resolved image brightness values ​​based on the instruction. In another particular implementation, when the projector receives an instruction from the processor and projects a virtual image onto the eyepiece, the projector sends spatially resolved image brightness values ​​to the processor. In another specific implementation, a light sensor positioned on or near the eyepiece detects spatially resolved image brightness values ​​and transmits them to a processor. In other embodiments, or in the same embodiment, the image information includes global image brightness values. The global image brightness values ​​may be associated with the entire system field of view (e.g., the average image brightness value of the entire virtual image).

[0064] In step 412, the portion of the system field of view that will be at least partially dimmed is determined based on detected information. The detected information may include light information detected during step 406, line-of-sight information detected during step 408, and / or image information detected during step 410. In some embodiments, the portion of the system field of view is equal to the entire system field of view. In various embodiments, the portion of the system field of view may be equal to 1%, 5%, 10%, 25%, 50%, or 75% of the system field of view, etc. In some embodiments, different types of information may be weighted differently when determining the portion that will be at least partially dimmed. For example, line-of-sight information, when available, may be weighted more heavily than light information and image information when determining the portion that will be at least partially dimmed. In one particular implementation, each type of information may be used independently to determine different portions of the system field of view that will be at least partially dimmed, and then the different portions may be combined into a single portion using AND or OR operations.

[0065] In step 414, multiple spatially decomposed dimming values ​​for a portion of the system's field of view are determined based on the detected information. In some embodiments, the dimming values ​​are determined using a formulaic approach based on the desired opacity or visibility of the virtual content. In one particular implementation, the visibility of the virtual content may be calculated using the following equation: [ka] In the formula, V is the visibility, and I max This is the brightness of a virtual image as indicated by the image information, and I backC is related to a light value associated with a world object, as indicated by light information (which may be modified by the determined dimming value), and C is the desired contrast (e.g., 100:1). For example, the visibility equation may be used to calculate a dimming value for a particular pixel location at each pixel location of the dimmer, using the brightness of the virtual image at that particular pixel location and the light value associated with the world object at that particular pixel location.

[0066] In step 416, the dimmer is adjusted to reduce the intensity of light associated with an object within a portion of the system field of view. For example, the dimmer may be adjusted so that the intensity of light associated with an object, which collides on each pixel location of the dimmer, is reduced according to a dimming value determined for that particular pixel location. As used in this disclosure, the steps of adjusting the dimmer may include initializing the dimmer, activating the dimmer, powering on the dimmer, modifying or changing a previously initialized, activated, and / or powered-on dimmer, and equivalents. In some embodiments, a processor may transmit data to the dimmer indicating both a portion of the system field of view and a plurality of spatially resolved dimming values.

[0067] In step 418, the projector is adjusted to adjust the brightness associated with the virtual image. For example, in some embodiments, it may be difficult to achieve the desired opacity or visibility of the virtual content without increasing or decreasing the brightness of the virtual object. In such embodiments, the brightness of the virtual image may be adjusted before, after, simultaneously with, or in parallel with adjusting the dimmer.

[0068] Figure 5 illustrates an AR device 500 comprising an eyepiece 502 and a pixelated dimming element 503 consisting of a spatial grid of dimming areas (i.e., pixels) that may have various levels of dimming independently of each other (i.e., they are independently variable). Each dimming area may have associated size (e.g., width and height) and associated spacing (e.g., pitch). As shown, the spatial grid of dimming areas may include one or more dark pixels 506 that provide complete dimming of incident light and one or more clear pixels 508 that provide complete transmission of incident light. Adjacent pixels within the pixelated dimming element 503 may be touching (e.g., when the pitch is equal to the width) or separated by a gap or channel (e.g., when the pitch is greater than the width).

[0069] In various embodiments, the pixelated dimming element 503 utilizes liquid crystal technology. Such technology typically includes a layer of liquid crystal material (e.g., having a nematic phase) that is aligned with one or more electrode layers so that the liquid crystal material can be reoriented in response to the electric field intensity applied to the pixel (e.g., by applying a potential difference across the liquid crystal layer using electrodes on the opposite side of the liquid crystal layer). Embodiments of liquid crystal modes include twisted nematic ("TN") or vertically aligned ("VA") liquid crystals. Electrically controlled birefringent ("ECB") liquid crystal modes can also be used. Liquid crystal phases other than nematic phases, such as ferroelectric liquid crystals, can also be used. In some embodiments, dye-doped or guest-host type liquid crystal materials can also be used.

[0070] Figure 6A depicts a front view of an exemplary optically transparent spatial light modulator ("SLM") or display assembly 603 for a see-through display system. Similarly, Figure 6B depicts a schematic cross-sectional view of the exemplary SLM or display assembly of Figure 6A. In some embodiments, the optically transparent SLM or display assembly 603 may form all or part of the outer cover of an augmented reality system. Assembly 603 may correspond to an optically transparent controllable dimming assembly similar to or comparable to one or more of the dimming assemblies, optically transparent LCDs, optically transparent OLED displays, and equivalents described herein. In some implementations, the assembly 603 in Figures 6A–6B may correspond to one or more of the components 203, 303a, 303B, and 503, respectively, as described above with reference to Figures 2A–2C, 3, and 5. Additional embodiments of the controllable dimming assembly architecture and control scheme are described in further detail in U.S. Provisional Patent Applications No. 62 / 725,993, No. 62 / 731,755, No. 62 / 858,252, and No. 62 / 870,896 (all of which are incorporated herein by reference as a whole).

[0071] In the embodiment shown in Figures 6A-6B, assembly 603 includes a liquid crystal layer 618 sandwiched between the outer electrode layer 616A and the inner electrode layer 616B, which in turn is sandwiched between the outer polarizer 612A and the inner polarizer 612B. The outer and inner polarizers 612A and 612B may be configured to linearly polarize unpolarized light passing through them. Assembly 603 includes an outer substrate layer 620A positioned between the outer polarizer 612A and the outer electrode layer 616A, and an inner substrate layer 620B positioned between the inner polarizer 612B and the inner electrode layer 616B. The substrate layers 620A and 620B support the electrode layers 616A and 616B and are typically formed from an optically transparent material such as glass or plastic. Assembly 603 further includes an outer optical retarder 614A (e.g., an A-plate) positioned between the outer polarizer 612A and the outer electrode layer 616A, and an inner optical retarder 614B (e.g., an A-plate) positioned between the inner polarizer 612B and the inner electrode layer 616B.

[0072] As described above, in some implementations, assembly 803 may include or correspond to an ECB cell. Advantageously, the ECB cell can be configured, for example, to modulate circularly polarized light, for example, to change the ellipticity of the circularly polarized light.

[0073] During operation, the outer polarizer 612A imparts a first polarization state (e.g., linear polarization along the vertical direction in Figure 6A) to the ambient light propagating through it toward the user's eye. Then, depending on its orientation, the liquid crystal molecules contained within the liquid crystal layer 618 further rotate / delay the polarized ambient light as it traverses the liquid crystal layer 618. For example, the liquid crystal layer 618 can rotate linear polarization so that its polarization plane differs from the polarization plane of the first polarization state. Alternatively, or in addition, the liquid crystal layer can delay the polarization, for example, converting linear polarization to elliptical or circular polarization. Generally, the amount of rotation / delay depends on the birefringence of the liquid crystal material, its orientation, and the thickness of the liquid crystal layer 618. The amount of rotation / delay also depends on the electric field applied to the liquid crystal layer 618, for example, by applying a potential difference across the outer and inner electrode layers 616A, 616B. The amount of polarization rotation imparted by the pair of electrode layers 616A, 616B and liquid crystal layer 618 can vary from pixel to pixel, depending on the voltage applied to the electrode layer at each individual pixel.

[0074] Polarization delay is also affected by the outer and inner optical retarders 614A and 614B. For example, the use of a quarter-wave plate as the outer optical retarder 614A delays the linearly polarized light transmitted by the polarizer 612A, converting the linearly polarized light into circularly polarized light, and the speed axis of the quarter-wave plate is appropriately oriented (e.g., at 45°) with respect to the axis of passage of the linear polarizer.

[0075] Finally, the inner polarizer 612B may transmit light in a second different polarization state (e.g., horizontal polarization) compared to the outer polarizer 612A. The second polarization state may be orthogonal to the polarization state imparted to the ambient light by the outer polarizer 612A. In situations where the cumulative effect of the liquid crystal layer 618 and the outer and / or inner optical retarders 614A, 614B rotates the polarization transmitted by the outer polarizer 612A, the inner polarizer 612B will transmit the light transmitted by the outer polarizer 612A, even though it is rotated by 90 degrees. Alternatively, if the cumulative effect of the liquid crystal layer 618 and the optical retarders 614A and 614B keeps the polarization state of the light from polarizer 612A unchanged, this will be blocked by the inner polarizer 612B. Therefore, the internal polarizer 612B can allow the portion of ambient light in the second polarization state to pass through it unaffected, and can attenuate the portion of ambient light in polarization states other than the second polarization state. The amount of polarization rotation can be controlled on a pixel-by-pixel basis by the electric field intensity applied to the liquid crystal layer at each pixel, thereby enabling the light transmission of device 603 to be controlled on a pixel-by-pixel basis.

[0076] In general, the pixel structure of the electrode layer can vary depending on, for example, the properties of the liquid crystal layer, the pixel size, etc. In some embodiments, one of the outer electrode layer 616A and the inner electrode layer 616B may correspond to a layer of individually addressable electrodes (i.e., pixels) arranged in a two-dimensional array. For example, in some embodiments, the inner electrode layer 616B may correspond to an array of pixel electrodes that, in conjunction with the outer electrode layer 616A, each selectively controlled by assembly 603 and capable of generating individual electric fields / voltages, may correspond to a single planar electrode. In some embodiments, one or both electrodes of the outer and inner electrode layers 616A, 616B may be made from an optically transparent conductive material such as indium tin oxide ("ITO").

[0077] As shown in Figures 6A-6B, assembly 603 also includes metal line traces or conductors 617a-n. Each pixel electrode in the array of pixel electrodes of assembly 603 is electrically coupled to a corresponding thin-film transistor ("TFT"), which in turn is electrically coupled to a corresponding pair of metal line traces or conductors in the plurality of metal line traces or conductors 617a-n. Such metal line traces or conductors are located within "transparent gap" regions between pixels (e.g., pixel electrodes in the inner electrode layer 616B) and are further electrically coupled to one or more circuits to drive or otherwise control the state of each pixel. In some embodiments, such one or more circuits may include a glass-on-chip ("COG") component 622. The COG component 622 may be located on a layer of glass in assembly 603, such as the inner glass layer 620B. In some implementations, the COG component 622 may be laterally offset from the array of pixels (e.g., the array of pixel electrodes in the inner electrode layer 616B). Thus, the COG component 622 of assembly 603 may be positioned outside the user's field of view ("FOV"), hidden by the housing or other components or combination thereof of the see-through display system. Pixels using an active switching element such as a TFT are referred to as "actively addressed."

[0078] Figure 7A illustrates an embodiment of the see-through display system 700 in a first state (state "A"). Similarly, Figure 7B illustrates the see-through display system 700 in a second state (state "B"), which is different from the first state (state "A"). As shown in Figures 7A-7B, the system 700 includes an eyepiece 702 and an optically transparent SLM or display assembly 703. In some embodiments, the eyepiece 702 in Figures 7A-7B corresponds to one or more of components 202, 302A, 302B, and 502, respectively, as described above with reference to Figures 2A-2C, 3, and 5. In some implementations, assembly 703 in Figures 7A–7B may correspond to one or more of components 203, 303a, 303B, 503, and 603, respectively, as described above with reference to Figures 2A–2C, 3, 5, and 6A–6B.

[0079] The eyepiece 702 of system 700 includes three waveguides 1210, 1220, and 1230. The three waveguides 1210, 1220, and 1230 may each correspond to, for example, different light colors and / or depths of virtual content. As shown in Figures 7A-7B, the eyepiece 702 further includes internal coupling optical elements 1212, 1222, and 1232, respectively, which are positioned on waveguides 1210, 1220, and 1230. The internal coupling optical elements 1212, 1222, and 1232 may each be configured to couple light into waveguides 1210, 1220, and 1230 for propagation via total internal reflection (TIR). In addition, the eyepiece 702 also includes externally coupled diffractive optical elements 1214, 1224, and 1234, respectively, positioned on waveguides 1210, 1220, and 1230. The externally coupled diffractive optical elements 1214, 1224, and 1234 may be configured to couple light out of waveguides 1210, 1220, and 1230 toward one or both eyes of a viewer of the system 700. As can be seen from Figure 7A, in the first state (state "A"), light is not coupled into or out of the eyepiece 702.

[0080] In the embodiment shown in Figure 7B, the system 700 is in a second distinct state (state "B") in which light (i) is coupled into waveguides 1210, 1220, and 1230 using internal coupling optical elements 1212, 1222, and 1232, (ii) propagates through waveguides 1210, 1220, and 1230 via total internal reflection (TIR), and (iii) is coupled out of waveguides 1210, 1220, and 1230 using external coupling diffractive optical elements 1214, 1224, and 1234. As each optical path 1240, 1242, and 1244 internally couples at locations 1212, 1222, and 1232, respectively, and collides with individual externally coupled diffracting optical elements 1214, 1224, or 1234 (light externally coupled from paths 1222 and 1232, not depicted) located on waveguides 1210, 1220, and 1230, it diffracts the light both toward the viewer and toward the world side of the device, away from the viewer. This light propagation is described as multiple beamlets, each propagating in two opposing directions: one toward the viewer represented by the luminous flux 3010 and the other away from the viewer represented by the luminous flux 3020.

[0081] As the luminous beam 3020 propagates away from the viewer, if it reflects from elements of the system along its path, these reflections can reach the viewer as stray light, potentially producing undesirable effects. For example, reflection of this light from the subsequent waveguide 1220 may interfere with the luminous beam 3010, increasing the blurring of the image projected by the system 700 and / or reducing contrast. Furthermore, in some situations, the luminous beam 3020 may reflect from one or more components of assembly 703, such as metal line traces or conductors, comparable to or similar to the metal line traces or conductors 617a-n of assembly 603 as described above with reference to Figures 6A-6B, which can produce "afterimage" images and other undesirable artifacts. By employing pupil expander technology, waveguide optical systems can further exacerbate these problems.

[0082] Figures 8A and 8B illustrate embodiments of the see-through display system 800 in a first state (state "A") and a second state (state "B") that is different from the first state (state "A"), respectively. As shown in Figures 8A-8B, the system 800 includes an eyepiece 702 and an optically transparent SLM 803. In some embodiments, the eyepiece 702 in Figures 8A-8B may correspond to the eyepiece 702 in Figures 7A-7B, but may also include an outer glass cover 1250A and an inner glass cover 1250B positioned on either side of the waveguide stack.

[0083] In some implementations, assembly 803 in Figures 8A–8B may correspond to one or more of assemblies 603 and 703 as described above with reference to Figures 6A–6B and 7A–7B, respectively, while the inner and outer optical retarders 614A and 614B are quarter-wave plates (QWPs) 624A and 624B, respectively. The outer and inner QWPs 624A and 624B serve to convert linearly polarized light passing through them into circularly polarized light. For example, light propagating from the viewer's environment toward the viewer may be linearly polarized as it passes through the outer polarizer 612A, and then circularly polarized as it passes through the outer QWP 624A. Similarly, light propagating toward assembly 803 away from the viewer, such as one or more portions of the luminous flux 3020, may become linearly polarized as it passes through the inner polarizer 612B, and then become circularly polarized as it passes through the inner QWP 624B. As can be seen from Figure 8A, in the first state (state "A"), the light is not coupled into or out of the eyepiece 702.

[0084] In the embodiment shown in Figure 8B, the system 800 is in a second distinct state (state "B"), where light is coupled outward from the eyepiece 702 in two directions: one toward the viewer represented by ray 3011 and the other away from the viewer represented by ray 3021. Rays 3011 and 3021 may represent portions of a luminous flux, similar to luminous fluxes 3010 and 3020 as described above with reference to Figure 7B. As shown in Figure 8B, as ray 3021 propagates away from the eyepiece 702 toward the assembly 803, ray 3021 becomes linearly polarized as it passes through the inner polarizer 612B, and then circularly polarized as it passes through the inner QWP 624B. Depending on whether the ray 3021 reaches one of the metal line traces or conductors of assembly 803 or beyond, it may be reflected back toward the eyepiece 702, which can effectively reverse the circular polarization of the ray 3021 (i.e., left-hand circular polarization becomes right-hand circular polarization upon reflection, and vice versa). On its way back toward the eyepiece 702, passing through the inner QWP 624B, the circular polarization is converted back to linear polarization, but polarized to be perpendicular to the state through which it passes the polarizer 612B. Thus, the reflected light is attenuated (e.g., blocked) by the polarizer 612B. In this way, system 800 reduces the effect of "afterimage" images that may be produced as a result of light from the eyepiece 702 being reflected back toward the viewer from the components of assembly 803.

[0085] In some embodiments, the inner optical retarder 614A is a quarter-wave plate, and the outer optical retarder 614B is an A-plate (e.g., a uniaxial birefringent film with a velocity axis in the plane of the plate) with a delay slightly different from the quarter-wave delay. For example, in some implementations, the liquid crystal may retain some residual birefringence, even under its lowest birefringence state. This can result, for example, from the orientation of liquid crystal molecules near the matching layer within the liquid crystal layer. In and near the matching layer, the liquid crystal molecules may retain their matching even in the presence of the maximum electric field intensity applied by the electrode structure. Such residual delay in the liquid crystal material can be compensated for by increasing the delay of the outer optical retarder 614B above the quarter-wave delay. For example, the outer optical retarder 614B can be an A-plate with a quarter-wave delay of 5 nm or more (e.g., up to 50 nm, 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more). Compensating for residual delay in the liquid crystal layer can reduce light leakage through a dynamic dimmer.

[0086] The speed axes of the inner and outer optical retarders are generally aligned with respect to the alignment direction of the liquid crystal layer and the through axes of the inner and outer polarizers so that the dynamic dimmer provides a large dynamic range with good attenuation in its darkest state. In some embodiments, the inner and outer optical retarders have their speed axes oriented at 45° with respect to the through axis of their adjacent polarizer. The speed axes of the inner and outer optical retarders can be oriented at 90° with respect to each other. In some embodiments, the speed axis of the outer optical retarder is oriented at 90° with respect to the alignment direction of the liquid crystal layer at the world-side boundary of the liquid crystal layer.

[0087] Generally, the performance of a dynamic dimmer is optimized for at least one light propagation direction at at least one wavelength. For example, the performance of a dynamic dimmer can be optimized for "on-axis" light, i.e., light incident normal to the layers of the stack forming the dynamic dimmer. In one embodiment, the performance of a dynamic dimmer is optimized for green light, for example, light with a wavelength of 550 nm. Furthermore, the performance of a dynamic dimmer may be optimized for one wavelength along one light propagation direction, but generally, a dimmer will be configured to provide adequate performance over a range of angles and wavelengths. For example, a dynamic dimmer can be configured to provide adequate performance (e.g., a dynamic range above a minimum performance threshold) over a range of light propagation angles equal to or larger than the field of view of a display. Furthermore, the performance can be adequate over a range of operating wavelengths (e.g., spanning the color gamut of a display). To achieve adequate performance over a range of wavelengths, some implementations may use achromatic optical components, such as achromatic optical retarders. Achromatic A-plates (e.g., achromatic quarter-wave plates) can be provided, for example, by using two or more different birefringent materials having different dispersions.

[0088] Figure 9 illustrates a further embodiment of the see-through display system 900. The system 900 in Figure 9 may correspond to the system 800 in Figures 8A-8B, but may further include an outer anti-reflective layer 626A and an inner anti-reflective layer 626B. The outer anti-reflective layer 626A may be positioned adjacent to the outer polarizer 612A, while the inner anti-reflective layer 626B may be positioned adjacent to the inner polarizer 612B. The outer and inner anti-reflective layers 626A and 626B may play a role in further reducing the presence of undesirable effects such as “afterimage” images by limiting the reflection of light so that it does not couple outward from the eyepiece 702. In some situations, at least some of such reflections may be the result of refractive index mismatches (i.e., Fresnel reflections) between different layers of the display system 900 or between the air and the layers of the display system 900. The anti-reflective layers can reduce such reflections. Various different suitable anti-reflective layers, including single-layer or multi-layer anti-reflective films, can be used. Such layers can be optimized for on-axial light or for light at some other non-normal incidence angle. Such layers can be optimized for one or more visible wavelengths. In some embodiments, the anti-reflective layer is optimized for light having wavelengths in the green portion of the visible spectrum, for example, wavelengths at or near the maximum photopic luminous sensitivity of the human eye. An example of an anti-reflective layer for use in an eyepiece is described in U.S. Patent Application No. 16 / 214,575, filed December 10, 2018, and published June 13, 2019, as U.S. Patent Publication No. 2019 / 0179057 (expressly incorporated herein in whole by reference).

[0089] Figure 10 illustrates yet another embodiment of the see-through display system 1000. The system 1000 in Figure 10 may correspond to the system 900 in Figure 9, but may further include a second outer QWP 634A and a second inner QWP 634B. The second outer QWP 634A is positioned adjacent to the outer polarizer 612A, while the second inner QWP 634B is positioned adjacent to the inner polarizer 612B. The second QWP 634A may further reduce the presence of undesirable effects such as “afterimage” images by modulating the polarization state of the light that has passed through the outer polarizer 612A, so that when reflected from one or more objects in the vicinity of the system 1000 (e.g., beyond assembly 803), the light travels away from the viewer so that the light is attenuated by the outer polarizer 612A. Similarly, the inner QWP634B may further reduce the presence of undesirable effects such as “afterimage” images by modulating the polarization state of the light that has passed through the inner polarizer 612B, so that when the light is reflected from one or more components of the system 1000 positioned between the inner polarizer 612B and the viewer, the light travels toward the viewer and is attenuated by the inner polarizer 612A.

[0090] Figure 11 illustrates another embodiment of the see-through display system 1100. The system 1100 in Figure 11 may correspond to the system 1000 in Figure 10, but may include a refractive index-matched layer 628 instead of component 626B. The refractive index-matched layer 628 may be a layer of material (e.g., gel or optical adhesive) having a refractive index comparable to or similar to the refractive index of either the second inner QWP 634B or the layer of assembly 803 closest to the eyepiece 702. Including a refractive index-matched layer may further reduce the presence of undesirable effects such as “afterimage” images by reducing Fresnel reflection of light from the eyepiece 702 incident on assembly 803.

[0091] In some implementations, the see-through display system may include some or all of the components from one or more of Figures 8A-11. Other configurations, including the see-through display system, with different combinations of components from one or more of Figures 8A-11, are also possible. While primarily described in the context of optically transparent spatial light modulators and displays, it should be understood that one or more of the configurations and techniques described herein may be utilized in other systems with see-through pixel arrays.

[0092] 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.

[0093] 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).

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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, or be operably coupled to, one or more mass storage devices for storing data, such as magnetic, magneto-optical disks, or optical disks, in order to receive data, or transfer data, or both. However, a computer is not required to have such devices. Suitable devices 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.

[0098] 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.

[0099] 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.

[0100] Figure 12 shows an exemplary computer system 1200, which includes a processor 1210, memory 1220, storage device 1230, and input / output device 1240. Components 1210, 1220, 1230, and 1240 can each be interconnected, for example, by a system bus 1250. The processor 1210 is capable of processing instructions for execution within the system 1200. In some implementations, the processor 1210 is a single-threaded processor, a multi-threaded processor, or another type of processor. The processor 1210 is capable of processing instructions stored in memory 1220 or on storage device 1230. Memory 1220 and storage device 1230 can store information within the system 1200.

[0101] The input / output device 1240 provides input / output operation for system 1200. In some implementations, the input / output device 1240 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 1260. In some implementations, mobile computing devices, mobile communication devices, and other devices may also be used.

[0102] The methods, systems, and devices discussed above are embodiments. Various configurations may omit, substitute, or add various procedures or components as needed. For example, in alternative configurations, the method may be carried out in a different order than described, and / or various steps may be added, omitted, and / or combined. Also, features described in relation to one configuration may be combined in various other configurations. Different aspects and elements of a configuration may be combined in a similar manner. Furthermore, technology is evolving, and therefore many of the elements are embodiments and do not limit the scope or claims of this disclosure.

[0103] Specific details are given in the description to provide a complete understanding of the exemplary configurations, including their implementation. However, the configurations may be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques are shown without unnecessary details to avoid obscuring the configurations. This description provides only exemplary configurations and does not limit the scope, availability, or configurations of the claims. Rather, the foregoing description of configurations will provide a useful description for implementing the techniques described to those skilled in the art. Various modifications may be made to the function and arrangement of the elements without departing from the spirit or scope of this disclosure.

[0104] While several exemplary configurations have been described, various modifications, alternative structures, and equivalents may be used without departing from the spirit of this disclosure. For example, the elements described herein may be components of a larger system, and other rules may take precedence over or modify them in a different way for the use of the art. Also, some steps may be taken before, during, or after the elements described herein are considered. Therefore, the foregoing description is not intended to restrict the scope of the claims.

[0105] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise. Thus, for example, a reference to “user” includes multiple such users, and a reference to “processor” includes one or more processors and their equivalents known to those skilled in the art, etc.

[0106] Furthermore, the words “comprise,” “comprising,” “contains,” “containing,” “include,” “including,” and “includes,” when used herein and in the following claims, are intended to specify the presence of the described feature, integer, component, or step, but they do not preclude the presence or addition of one or more other features, integers, components, steps, actions, or groups.

[0107] Furthermore, the examples and embodiments described herein are for illustrative purposes only, and it should be understood that various modifications or changes in light thereof are suggested to those skilled in the art and fall within the spirit, authority, and scope of the appended claims.

Claims

1. It is a method, The method includes using a dynamic dimming assembly to modulate the intensity of light transmitted parallel to the optical axis from the world side of the dynamic dimming assembly to the user side of the dynamic dimming assembly, wherein the world side is configured to face away from the user, and the user side is configured to face toward the user. The dynamic dimming assembly is The first electrode layer and The second electrode layer, A liquid crystal layer disposed between the first electrode layer and the second electrode layer, A circular polarizer arranged on the user side of the liquid crystal layer, A linear polarizer located on the world side of the liquid crystal layer, An optical retarder arranged between the liquid crystal layer and the linear polarizer Equipped with, Modulating the intensity of the aforementioned light is Using the aforementioned linear polarizer, the light is linearly polarized, Using the first electrode layer, the second electrode layer, and the liquid crystal layer, at least one of the following is performed: rotate the polarization of the light, or take the polarization of the light into consideration. Using the circular polarizer, the light is made circularly polarized. Methods that include...

2. The method according to claim 1, wherein at least one of rotating the polarization of the light or considering the polarization of the light includes applying a voltage to at least one of the first electrode layer or the second electrode layer.

3. The liquid crystal layer comprises a plurality of pixels that are actively addressed, The method according to claim 2, wherein applying the voltage to at least one of the first electrode layer or the second electrode layer causes the polarization of the light to rotate pixel by pixel by the first electrode layer, the second electrode layer and the liquid crystal layer.

4. The method according to claim 1, further comprising transmitting light from a see-through display located on the user side of the dynamic dimming assembly to the user.

5. The method according to claim 4, wherein at least a portion of the light transmitted from the see-through display to the user is received from one or more optical projectors.

6. The method according to claim 4, wherein the light from the see-through display represents augmented reality content.

7. The method according to claim 4, wherein the light is transmitted through one or more refractive index matching layers arranged between the see-through display and the dynamic dimming assembly.

8. The circular polarizer comprises a second linear polarizer and a first quarter-wave plate. The method according to claim 1, wherein the circular polarization of the light is performed by using the second linear polarizer and the first quarter-wave plate.

9. The aforementioned optical retarder is A second quarter-wave plate, or A-plate with a delay greater than that of the first quarter-wave plate. The method according to claim 8, wherein at least one of the following is the method according to claim 8.

10. The dynamic dimming assembly comprises an A-plate arranged between the linear polarizer on the world side of the liquid crystal layer and the liquid crystal layer, The method according to claim 1, wherein the light is transmitted from the linear polarizer to the liquid crystal layer through the A-plate.

11. The dynamic dimming assembly comprises one or more anti-reflective layers, The method according to claim 1, wherein the light is transmitted through the one or more anti-reflective layers.

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