Polarization compensation for wire grid polarizers for head mounted display systems

Abstract

The present disclosure generally relates to techniques for improving performance and efficiency of optical systems, such as optical systems for using head mounted display systems. The optical system of the present disclosure may include a polarizing reflective refractive optic, or a "pancake optic" utilizing a wire grid polarizer as a reflective polarizer. Wire grid polarizers may not be uniformly performed at wavelengths or at varying angles of incidence. To improve performance, a spatially varying polarizer is provided in an optical system for providing polarization compensation for the wire grid polarizer such that the wire grid polarizer appears more uniform over the wavelength and / or over the angle of incidence (e.g., on and off-axis). The spatially varying polarizer may be formed from a liquid crystal material, such as a multi-twist retarder.

Description

Technical Field

[0001] The present disclosure relates generally to optical systems and, more particularly, to improving the efficiency and performance of optical systems for head mounted display systems. Background Art

[0002] The current generation of virtual reality (VR) experiences are created using a head-mounted display (HMD) that can be tethered to a stationary computer (e.g., a personal computer (PC), laptop, or game console), can be combined and / or integrated with a smartphone and / or its associated display, or can be standalone. Typically, an HMD is a display device worn on the user's head that has a small display device in front of one eye (monocular HMD) or each eye (binocular HMD). The display unit is typically miniaturized and can include, for example, a CRT, LCD, liquid crystal on silicon (LCoS), OLED technology, or a laser scanning beam display. Binocular HMDs have the ability to display a different image to each eye. This capability is used to display stereoscopic images.

[0003] With the development of smart phones, high-definition televisions, and other electronic devices, the demand for displays with enhanced performance has increased. Virtual reality and augmented reality systems, especially those using HMDs, have further increased this demand. Virtual reality systems typically completely encase the wearer's eyes and replace the actual or physical view (or actual reality) with a "virtual" reality in front of the wearer; while augmented reality systems typically provide a translucent or transparent covering of one or more screens in front of the wearer's eyes so that the actual view is augmented with additional information; and mediated reality systems can similarly present such information to the viewer that combines real-world elements with virtual elements.

[0004] However, such head mounted displays (with a reduced distance between the viewer's eyes and the display and typically with a completely blurred field of view) increase the performance requirements of the display in a way that conventional displays cannot meet, let alone achieve these performance requirements at a cost-effective level. Microdisplays (such as OLED microdisplays) are much smaller than conventional displays, but involve additional challenges. For example, microdisplays require lenses with very short focal lengths. In addition, because the user's eye pupil size is fixed, the F / # of the lenses of an HMD using a microdisplay is reduced, which tends to increase the aberrations of a particular lens system. In addition, microdisplays have small pixels. This increases the spatial resolution of the HMD optics and also increases the challenges of designing and manufacturing lenses for such HMDs. Summary of the invention

[0005] The head-mounted display system can be summarized as including a display subsystem and an optical system, wherein the display subsystem is used to generate an image including linearly polarized light, the optical system including: a lens element that receives light from the display subsystem, the lens element including a partially reflective surface; a wire grid polarizer that receives light from the lens element; a quarter wave plate located between the lens element and the wire grid polarizer; and a spatially varying polarizer located between the display subsystem and the lens element, the spatially varying polarizer having a retardation that varies across an optical window of the spatially varying polarizer to compensate for off-axis light incident on the wire grid polarizer.

[0006] The spatially varying polarizer may include a multi-twist retarder. The spatially varying polarizer may provide a quarter wave retardation at the center of the optical window and may gradually reduce the retardation toward the periphery of the optical window. The spatially varying polarizer may provide an eighth wave retardation at the periphery of the window. The spatially varying polarizer may provide a first retardation at the center of the optical window and may provide a second retardation at the periphery of the optical window, wherein the second retardation is less than the first retardation. The retardation of the spatially varying polarizer may vary linearly or nonlinearly across the optical window.

[0007] The head mounted display system may also include a control circuit operably coupled to the spatially varying polarizer, the control circuit operative to selectively adjust the delay provided by the spatially varying polarizer.

[0008] The head-mounted display system can be summarized as including a display subsystem and an optical system, wherein the display subsystem is used to generate an image including linearly polarized light, the optical system including: a quarter wave plate that receives light from the display subsystem; a lens element that receives light from the quarter wave plate, the lens element including a partially reflective surface; a wire grid polarizer that receives light from the lens element; and a spatially varying polarizer located between the lens element and the wire grid polarizer, the spatially varying polarizer having a retardation that varies across an optical window of the spatially varying polarizer to compensate for off-axis light incident on the wire grid polarizer.

[0009] The spatially varying polarizer may include a multi-twist retarder. The spatially varying polarizer may provide a quarter wave retardation at the center of the optical window and may gradually reduce the retardation toward the periphery of the optical window. The spatially varying polarizer may provide an eighth wave retardation at the periphery of the window. The spatially varying polarizer may provide a first retardation at the center of the optical window and may provide a second retardation at the periphery of the optical window, wherein the second retardation is less than the first retardation. The retardation of the spatially varying polarizer may vary linearly or nonlinearly across the optical window.

[0010] The head mounted display system may also include a control circuit operably coupled to the spatially varying polarizer, the control circuit operative to selectively adjust the delay provided by the spatially varying polarizer.

[0011] The head-mounted display system can be summarized as including a first and a second near-eye display system, each of the first and second near-eye display systems including a display subsystem and an optical subsystem, the display subsystem is used to generate an image including linearly polarized light, the optical subsystem including: a lens element, which receives light from the display subsystem, the lens element including a partially reflective surface; a wire grid polarizer, which receives light from the lens element; a quarter wave plate, which is located between the lens element and the wire grid polarizer; and a spatially varying polarizer, which is located between the display subsystem and the lens element, the spatially varying polarizer having a retardation that varies on an optical window of the spatially varying polarizer to compensate for off-axis light incident on the wire grid polarizer.

[0012] The spatially varying polarizer may include a multi-twist retarder.The spatially varying polarizer may provide a quarter wave retardation at the center of the optical window and may gradually decrease the retardation toward the periphery of the optical window.

[0013] The spatially varying polarizer can provide an eighth wave retardation at the periphery of the window. The spatially varying polarizer can provide a first retardation at the center of the optical window and can provide a second retardation at the periphery of the optical window. The retardation of the spatially varying polarizer can vary linearly or nonlinearly across the optical window. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the drawings, the same reference numerals represent similar elements or actions. The sizes and relative positions of the elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the readability of the drawings. In addition, the particular shapes of the elements shown in the drawings are not necessarily intended to convey any information about the actual shape of the particular element, and may be selected only for ease of identification in the drawings.

[0015] Figure 1 is a schematic diagram of a networked environment that includes one or more systems suitable for performing at least some of the techniques described in this disclosure.

[0016] Figure 2 is a diagram illustrating an example environment in which at least some of the described techniques are used with an example head-mounted display device that is tethered to a video rendering computing system and provides virtual reality presentation to a user.

[0017] Figure 3 is a front view of an exemplary HMD device with a binocular display subsystem.

[0018] Figure 4 A top view of an HMD device with a binocular display subsystem and various sensors according to an exemplary embodiment of the present disclosure is shown.

[0019] Figure 5is a cross-sectional view of an HMD device showing a display subsystem and its optical system according to one non-limiting exemplary embodiment.

[0020] Figure 6 According to a non-limiting exemplary embodiment Figure 5 Plan view of an exemplary spatially varying polarizer for the optical system shown. DETAILED DESCRIPTION

[0021] In the following description, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. However, one skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other cases, well-known structures associated with computer systems, server computers, and / or communication networks are not shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0022] Throughout the specification and the appended claims, the word "comprising" is synonymous with "including" and is inclusive or open-ended (ie, does not exclude other unrecited elements or methodological acts) unless the context requires otherwise.

[0023] Throughout this specification, reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0025] The titles and abstracts of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0026] The present disclosure generally relates to techniques for improving the performance and efficiency of optical systems, such as optical systems for use with head-mounted display systems. The optical systems of the present disclosure may include polarized catadioptric optics, or "pancake optics" utilizing a wire grid polarizer as a reflective polarizer. Wire grid polarizers may not perform uniformly over wavelength or over varying angles of incidence. In at least some embodiments of the present disclosure, a spatially varying polarizer is provided in the optical system, which is used to provide polarization compensation for the wire grid polarizer so that the wire grid polarizer performs more uniformly over wavelength and / or angles of incidence (e.g., on-axis and off-axis). The spatially varying polarizer may be formed by a multi-twist retarder, as discussed further below.

[0027] First, refer to Figures 1 to 4 Discuss an exemplary head mounted display device suitable for use with the techniques described herein. Then, refer to Figure 5 and Figure 6 Exemplary embodiments of display systems that include features of the present disclosure are discussed.

[0028] Exemplary head mounted display system and environment

[0029] Figure 1 1 is a schematic diagram of a networked environment 100 that includes a local media rendering (LMR) system 110 (e.g., a gaming system) that includes a local computing system 120 and a display device 180 (e.g., an HMD device with two display panels) that is suitable for performing at least some of the techniques described herein. Figure 1 In the illustrated embodiment, the local computing system 120 is connected to the computer via a transmission link 115 (which may be wired or tethered, for example, via a Figure 2 The local computing system 120 is communicatively connected to the display device 180 by one or more cables (cable 220) shown, or alternatively may be wireless. In other embodiments, whether in addition to or in lieu of the HMD device 180, the local computing system 120 may provide the encoded image data for display to a panel display device (e.g., a television, console, or monitor) via a wired or wireless link, and the display devices each include one or more addressable pixel arrays. In various embodiments, the local computing system 120 may include a general-purpose computing system; a game console; a video stream processing device; a mobile computing device (e.g., a cellular phone, PDA, or other mobile device); a VR or AR processing device; or other computing system.

[0030] In the illustrated embodiment, the local computing system 120 has components including one or more hardware processors (e.g., a centralized processing unit or CPU) 125, memory 130, various I / O (input / output) hardware components 127 (e.g., a keyboard, a mouse, one or more game controllers, speakers, a microphone, an IR transmitter and / or receiver, etc.), a video subsystem 140 including one or more dedicated hardware processors (e.g., a graphics processing unit or GPU) 144 and video memory (VRAM) 148, a computer-readable storage space 150, and a network connection 160. Also in the illustrated embodiment, an embodiment of an eye tracking subsystem 135 is executed in the memory 130 in order to perform at least some of the described techniques, such as by using the CPU 125 and / or GPU 144 to perform automated operations for implementing those described techniques, and the memory 130 may optionally further execute one or more other programs 133 (e.g., to generate video or other images to be displayed, such as a game program). As part of automated operation to implement at least some of the techniques described herein, the eye tracking subsystem 135 and / or program 133 executed in memory 130 may store or retrieve various types of data, including those in an exemplary database data structure of storage space 150; in this example, the data used may include various types of image data information 154 in a database (DB), various types of application data 152 in the DB, various types of configuration data 157 in the DB, and may include additional information such as system data or other information.

[0031] In the depicted embodiment, the LMR system 110 is also communicatively connected via one or more computer networks 101 and network links 102 to an exemplary network-accessible media content provider 190, which may further provide content (whether in addition to or in lieu of the image generation program 133) to the LMR system 110 for display. The media content provider 190 may include one or more computing systems (not shown), each of which may have components similar to those of the local computing system 120, including one or more hardware processors, I / O components, local storage devices, and memory, although some details are not shown for the network-accessible media content providers for the sake of brevity.

[0032] It should be understood that although Figure 1In the illustrated embodiment, the display device 180 is described as being distinct and separate from the local computing system 120, but in some embodiments, some or all components of the local media rendering system 110 may be integrated or housed within a single device, such as a mobile gaming device, a portable VR entertainment system, an HMD device, etc. In such an embodiment, the transmission link 115 may, for example, include one or more system buses and / or video bus architectures.

[0033] As an example involving operations performed locally by the local media rendering system 120, assume that the local computing system is a gaming computing system such that the application data 152 includes one or more gaming applications executed by the CPU 125 using the memory 130, and assume that various video frame display data is generated and / or processed by the image generation program 133, such as in conjunction with the GPU 144 of the video subsystem 140. In order to provide a high-quality gaming experience, a large amount of video frame data (corresponding to a high image resolution for each video frame, and a high "frame rate" of approximately 60-180 such video frames per second) is generated by the local computing system 120 and provided to the display device 180 via the wired or wireless transmission link 115.

[0034] It should also be understood that computing system 120 and display device 180 are only illustrative and are not intended to limit the scope of the present disclosure. Computing system 120 may alternatively include multiple interactive computing systems or devices, and may be connected to other devices not shown, including through one or more networks such as the Internet, via the Web, or via a dedicated network (e.g., a mobile communication network, etc.). More generally, a computing system or other computing node may include any combination of hardware or software that can interact and perform the functions of the type, including but not limited to desktop or other computers, game systems, database servers, network storage devices and other network devices, PDAs, cellular phones, wireless phones, pagers, electronic organizers, Internet appliances, TV-based systems (e.g., using set-top boxes and / or personal / digital video recorders) and various other consumer products including appropriate communication capabilities. Display device 180 may similarly include one or more devices with one or more display panels of various types and forms, and optionally include various other hardware and / or software components.

[0035] It should also be understood that although various items are shown as being stored in memory or on storage space when used, these items or portions thereof may be transferred between memory and other storage devices for purposes of memory management or data integrity. Thus, in some embodiments, some or all of the described techniques may be performed by hardware including one or more processors or other configured hardware circuits or memory or storage space, such as when configured by one or more software programs and / or data structures (e.g., by executing software instructions of one or more software programs and / or by storing such software instructions and / or data structures). Some or all of the components, systems, and data structures may also be stored (e.g., as software instructions or structured data) on a non-transitory computer-readable storage medium (e.g., a hard disk or flash drive or other non-volatile storage device), a volatile or non-volatile memory (e.g., RAM), a network storage device, or a portable media article to be read by an appropriate drive (e.g., a DVD disk, a CD disk, an optical disk, etc.) or through an appropriate connection. In some embodiments, the systems, components, and data structures may also be transmitted as generated data signals (e.g., as part of a carrier wave or other analog or digital propagation signal) on various computer-readable transmission media, including wireless-based and wired / cable-based media, and the systems, components, and data structures may take various forms (e.g., as part of a single or multiplexed analog signal, or as multiple discrete digital packets or frames). In other embodiments, such computer program products may also take other forms. Therefore, the present disclosure may be implemented with other computer system configurations.

[0036] Figure 2 An exemplary environment 200 is shown in which at least some of the described techniques are used with an exemplary HMD device 202, which is connected to a video rendering computing system 204 via a tethered connection 220 (or a wireless connection in other embodiments) to provide virtual reality display to a human user 206. The user wears the HMD device 202 and receives displayed information of a simulated environment different from the actual physical environment from the computing system 204 through the HMD device, wherein the computing system acts as an image rendering system that provides images of the simulated environment to the HMD device for display to the user, such as images generated by a game program and / or other software program executed on the computing system. In this example, the user is also able to move within a tracked volume 201 of the actual physical environment 200, and may also have one or more I / O (input / output) devices that allow the user to further interact with the simulated environment, which in this example include handheld controllers 208 and 210.

[0037] In the illustrated example, the environment 200 may include one or more base stations 214 (two are shown, labeled base stations 214a and 214b), which may help track the HMD device 202 or controllers 208 and 210. As the user moves the position of the HMD device 202 or changes the orientation of the HMD device 202, the position of the HMD device is tracked to allow the corresponding portion of the simulated environment to be displayed to the user on the HMD device, and the controllers 208 and 210 may also use similar techniques to track the position of the controller (and optionally use this information to help determine or verify the position of the HMD device). After the tracked position of the HMD device 202 is known, the corresponding information is sent to the computing system 204 via the tether 220 or wirelessly, which uses the tracked position information to generate one or more subsequent images of the simulated environment for display to the user.

[0038] A variety of different position tracking methods may be used in various embodiments of the present disclosure, including but not limited to acoustic tracking, inertial tracking, magnetic tracking, optical tracking, combinations thereof, and the like.

[0039] In at least some embodiments, the HMD device 202 may include one or more optical receivers or sensors that may be used to implement tracking functionality or other aspects of the present disclosure. For example, the base stations 214 may each scan an optical signal across the tracking volume 201. Each base station 214 may generate more than one optical signal, as required by each particular embodiment. For example, while a single base station 214 is typically sufficient for six-degree-of-freedom tracking, in some embodiments, multiple base stations (e.g., base stations 214a, 214b) may be required or desired to provide robust room-scale tracking for the HMD device and surrounding devices. In this example, the optical receiver is incorporated into the HMD device 202 and / or other tracked objects (e.g., controllers 208 and 210). In at least some embodiments, the optical receiver may be paired with an accelerometer and gyroscope inertial measurement unit (IMU) on each tracked device to support low-latency sensor fusion.

[0040] In at least some embodiments, each base station 214 includes two rotors that sweep linear beams across tracking volume 201 on orthogonal axes. At the beginning of each sweep cycle, base station 214 can transmit an omnidirectional light pulse (referred to as a "sync signal") that is visible to all sensors on the tracked object. Thus, each sensor calculates a unique angular position in the swept volume by timing the duration between the sync signal and the beam signal. The distance and direction of the sensors can be resolved using multiple sensors fixed to a single rigid body.

[0041] One or more sensors located on the tracked object (e.g., HMD device 202, controllers 208, and 210) may include an optoelectronic device capable of detecting modulated light from the rotor. For visible light or near infrared (NIR) light, a silicon photodiode and appropriate amplifier / detector circuitry may be used. Because environment 200 may contain static and time-varying signals (optical noise) having wavelengths similar to the signal of base station 214, in at least some embodiments, the base station light may be modulated in such a way that it is easily distinguished from any interfering signals and / or that radiation of any wavelength other than the base station signal is easily filtered from the sensor.

[0042] Inside-out tracking is also a type of position tracking that can be used to track the position of the HMD device 202 and / or other objects (e.g., controllers 208 and 210, tablet computers, smartphones). Inside-out tracking differs from outside-in tracking in the location of the camera or other sensor used to determine the position of the HMD. For inside-out tracking, the camera or sensor is located on the HMD or on the tracked object; whereas in outside-out tracking, the camera or sensor is placed at a fixed location in the environment.

[0043] An HMD utilizing inside-out tracking utilizes one or more cameras to “look out” to determine how its position has changed relative to the environment. As the HMD moves, the sensors readjust their position in the room, and the virtual environment responds accordingly in real time. This type of positional tracking can be implemented with or without markers placed in the environment. Cameras placed on the HMD observe features of the surrounding environment. When markers are used, the markers are designed to be easily detected by the tracking system and are placed in specific areas. With “markerless” inside-out tracking, the HMD system uses unique features (e.g., natural features) that are initially present in the environment to determine position and orientation. The HMD system’s algorithms recognize specific images or shapes and use them to calculate the device’s position in space. Data from accelerometers and gyroscopes can also be used to increase the accuracy of positional tracking.

[0044] Figure 3 Information 300 showing a front view of an exemplary HMD device 344 when worn on the head of a user 342. The HMD device 344 includes a front-facing structure 343 supporting a front-facing or forward-facing camera 346 and a plurality of sensors 348a-348d (collectively, 348) of one or more types. As one example, some or all of the sensors 348 (e.g., light sensors) can help determine the position and orientation of the device 344 in space to detect and use information from one or more external devices (not shown, for example, Figure 2344). As shown, the forward camera 346 and sensor 348 are directed forward toward the actual scene or environment (not shown) in which the user 342 operates the HMD device 344. The actual physical environment may include, for example, one or more objects (e.g., walls, ceilings, furniture, stairs, cars, trees, tracking markers, or any other type of object). The specific number of sensors 348 may be less than or more than the number of sensors shown. The HMD device 344 may also include one or more additional components that are not attached to the forward-facing structure (e.g., inside the HMD device), such as an IMU (inertial measurement unit) 347, an electronic device that measures and reports specific forces, angular rates, and / or magnetic fields around the HMD device (e.g., using a combination of accelerometers and gyroscopes, and optionally using a magnetometer) of the HMD device 344. The HMD device may also include additional components not shown, including one or more display panels and optical lens systems oriented toward the user's eyes (not shown), and the HMD device may optionally have one or more internal motors connected to change the alignment or other positioning of the one or more optical lens systems and / or display panels within the HMD device, as described below with respect to Figure 4 As discussed in more detail.

[0045] The example of the HMD device 344 shown is supported on the head of the user 342 based at least in part on one or more straps 345 connected to the housing of the HMD device 344 and extending in whole or in part around the user's head. Although not shown here, the HMD device 344 may also have one or more external motors, for example, connected to one or more straps 345, and the automatic corrective action may include using such motors to adjust such straps to change the alignment or other positioning of the HMD device on the user's head. It should be understood that the HMD device may include other support structures (e.g., nose fittings, chin straps, etc.) not shown here, whether in addition to or in lieu of the straps shown; and some embodiments may include motors connected to one or more such other support structures to similarly adjust their shape and / or position to change the alignment or other positioning of the HMD device on the user's head. Other display devices that are not secured to a user's head may be similarly connected to one or more structures, or portions thereof, that affect the positioning of the display device, and may include motors or other mechanical actuators in at least some embodiments to similarly change their shape and / or position to thereby change the alignment or other positioning of the display device relative to one or more pupils of one or more users of the display device.

[0046] Figure 4 A simplified top plan view 400 of an HMD device 405 is shown including a pair of near-eye display systems 402 and 404. The HMD device 405 may be, for example, Figures 1 to 3 The same or similar HMD devices as those shown in or HMD devices different therefrom, and the HMD devices discussed herein can be further used in the examples discussed below. Figure 4 The near-eye display systems 402 and 404 include display panels 406 and 408 (e.g., OLED microdisplays, LCD displays), respectively, and optical lens systems 410 and 412, each having one or more optical lenses. The display systems 402 and 404 can be mounted to or otherwise positioned within a housing (or frame) 414 that includes a front-facing portion 416 (e.g., with a Figure 3 The housing 414 is a housing 414 that is the same or similar to the front-facing surface 343 of the housing 414, a left temple 418, a right temple 420, and an inner surface 421 that contacts or is close to the face of a user 424 as a wearer when the user wears the HMD device. The two display systems 402 and 404 can be fixed to the housing 414 in an eyeglass arrangement in which the eyeglass device can be worn on the head 422 of the user 424 as a wearer, wherein the left temple 418 and the right temple 420 rest on the user's ears 426 and 428, respectively, and the nose fitting 492 can rest on the user's nose 430. Figure 4 In the example of FIG. 4 , the HMD device 405 can be partially or fully supported on the user's head by the nose display and / or the temples on the left and right ears, although in some embodiments a strap (not shown) or other structure can be used to secure the HMD device to the user's head, such as Figure 2 and Figure 3 . The shape and size of the housing 414 can be designed to position each of the two optical lens systems 410 and 412 in front of one of the user's eyes 432 and 434, respectively, so that the target position of each pupil 494 is vertically centered and horizontally centered in front of the corresponding optical lens system and / or display panel. Although the housing 414 is shown in a simplified manner similar to glasses for illustrative purposes, it should be understood that more complex structures (e.g., goggles, integrated headbands, helmets, straps, etc.) can actually be used to support and position the display systems 402 and 404 on the head 422 of the user 424.

[0047] Figure 4 The HMD device 405 and other HMD devices discussed herein are capable of presenting virtual reality displays to a user, for example through corresponding video presented at a display rate such as 30 or 60 or 90 frames (or images) per second, while other embodiments of similar systems can present augmented reality displays to a user. Figure 4Each of the displays 406 and 408 can generate light that is transmitted and focused onto the eyes 432 and 434 of the user 424 through the corresponding optical lens systems 410 and 412, respectively. The pupil 494 of each eye (through which light enters the eye) typically has a pupil size ranging from 2 mm (millimeters) in diameter in very bright conditions to as much as 8 mm in dark conditions, while the larger iris containing the pupil can have a size of about 12 mm - the pupil (and closed iris) can also typically move several millimeters in the horizontal and / or vertical direction within the visible part of the eye under an open eyelid, which will also cause the pupil to move to different depths from the optical lenses or other physical elements of the display for different horizontal and vertical positions as the eyeball rotates about its center (forming a three-dimensional volume in which the pupil can move). The light entering the user's pupil is viewed by the user 424 as an image and / or video. In some embodiments, the distance between each of optical lens systems 410 and 412 and the user's eyes 432 and 434 can be relatively short (e.g., less than 30 mm, less than 20 mm), which advantageously makes the HMD device appear brighter to the user because the weight of the optical lens system and the display system is relatively close to the user's face, and this can also provide a larger field of view to the user. Although not shown here, some embodiments of such an HMD device can include various additional internal and / or external sensors.

[0048] In the illustrated embodiment, Figure 4 The HMD device 405 also includes hardware sensors and additional components, such as one or more accelerometers and / or gyroscopes 490 (e.g., as part of one or more IMU units). As discussed in more detail elsewhere herein, the values ​​from the accelerometers and / or gyroscopes can be used to locally determine the orientation of the HMD device. In addition, the HMD device 405 may include one or more forward-facing cameras, such as a camera 485 outside the forward-facing portion 416, and its information can be used as part of the operation of the HMD device, such as for providing AR functions or positioning functions. In addition, the HMD device 405 may also include other components 475 (e.g., electronic circuits for controlling the display of images on the display panels 406 and 408, internal memory, one or more batteries, location tracking devices that interact with external base stations, etc.), as discussed in more detail elsewhere herein. Other embodiments may not include one or more of the components 475, 485, and / or 490. Although not shown here, some embodiments of such HMD devices may include various additional internal and / or external sensors to track various other types of motion and positions of the user's body, eyes, controllers, etc.

[0049] In the embodiment shown, Figure 4The HMD device 405 of the embodiment also includes hardware sensors and additional components that can be used by the disclosed embodiments as part of the described techniques for determining the user's pupils or gaze direction, which can be provided to one or more components associated with the HMD device for use, as discussed elsewhere herein. The hardware sensors in this example include one or more eye tracking assemblies 472 of the eye tracking subsystem, which are mounted on or near the display panels 406 and 408 and / or on the inner surface 421 located near the optical lens systems 410 and 412 for obtaining information about the actual position of the user's pupils 494, such as for each pupil separately in this example.

[0050] Each eye tracking assembly 472 may include one or more light sources (e.g., IR LEDs) and one or more light detectors (e.g., silicon photodiodes). Figure 4 4, but it should be understood that a different number of eye tracking assemblies may actually be provided. In some embodiments, a total of eight eye tracking assemblies 472 are provided, with four eye tracking assemblies provided for each eye of user 424. In addition, in at least some embodiments, each eye tracking assembly includes a light source directed toward one of eyes 432 and 434 of user 424, a light detector positioned to receive light reflected by the user's corresponding eye, and a polarizer positioned and configured to prevent light reflected via specular reflection from being applied to the light detector.

[0051] As discussed in greater detail elsewhere herein, information from eye tracking assembly 472 can be used to determine and track the user's gaze direction during use of HMD device 405. Additionally, in at least some embodiments, HMD device 405 can include one or more internal motors 438 (or other movement mechanisms) that can be used to move 439 the alignment and / or other positioning (e.g., in vertical, horizontal left-right, and / or horizontal front-to-back directions) of one or more optical lens systems 410 and 412 and / or display panels 406 and 408 within the housing of HMD device 405, e.g., to personalize or otherwise adjust a target pupil location for one or both of near-eye display systems 402 and 404 to correspond to an actual location of one or both of pupils 494. Such motors 438 can be controlled, for example, by a user manipulating one or more controls 437 on housing 414 and / or by a user manipulating one or more associated separate I / O controls (not shown). In other embodiments, HMD device 405 can control the alignment and / or other positioning of optical lens systems 410 and 412 and / or display panels 406 and 408 without requiring such motor 438, such as by using an adjustable positioning mechanism (e.g., a screw, a slider, a ratchet, etc.) that can be manually changed by a user using control 437. Figure 4 Motor 438 is shown for only one of the near-eye display systems, but in some embodiments, each near-eye display system can have its own one or more motors, and in some embodiments, one or more motors can be used to control (e.g., independently) each of multiple near-eye display systems.

[0052] While the described techniques may be used in some embodiments with a display system similar to that shown, other types of display systems may also be used in other embodiments, including use with a single optical lens and display device, or use with multiple such optical lenses and display devices. Non-exclusive examples of other such devices include cameras, telescopes, microscopes, binoculars, spotting mirrors, measuring scopes, and the like. In addition, the described techniques may be used with various display panels or other display devices that emit light to form an image, as discussed elsewhere herein, where one or more users view the image through one or more optical lenses. In other embodiments, a user may view one or more images generated in a manner that excludes the display panel, such as on a surface that partially or completely reflects light from another light source (e.g., a laser scanning beam), through one or more optical lenses.

[0053] Exemplary Display System

[0054] Figure 5FIG. 5 is a cross-sectional side view of a head mounted display system 500, which includes a display system 502 and an optical system 504 supported by a support structure 506, such as a housing, a helmet, goggles, glasses, or other headwear. Figure 5 The support structure 506 supports the display system 502 and the optical system 504 in front of the user's eye (e.g., eye 510) when viewing the system in the Z-axis direction indicated by the arrow 512. The control circuit 514 can optionally be coupled to the optical system 504 or one or more components of the display system 502, as discussed elsewhere herein. As an example, the display system 502 and the optical system 504 can be similar to those described above with reference to Figure 4 The display systems and optical systems discussed are similar or identical. Display system 502 and optical system 504 may be used to display images to user 510. As discussed further below, optical system 504 may utilize catadioptric or "pancake" optics to provide images from display system 502 to user's eye 510. The spacing and size of components of head mounted display system 400 may be different than shown. As an example, components shown as being spaced apart from one another may be positioned adjacent to one another in a different order, and so forth.

[0055] Display system 502 includes an image source, such as a pixel array 516. Pixel array 516 may include a two-dimensional array of pixels that emit light. As non-limiting examples, pixel array 516 may include a liquid crystal display (LCD), a liquid crystal on silicon (LCoS) display, an organic light emitting diode (OLED) display, etc.

[0056] Linear polarizer 518 may be located in front of pixel array 516 to provide polarized light from pixel array 516. In at least some embodiments, pixel array 516 may be designed to generate linearly polarized light, so that linear polarizer 518 may be omitted. As an example, linear polarizer 518 may have a shape similar to Figure 5 The X-axis shown is aligned with the transmission axis or through axis.

[0057] The optical system 504 may include a spatially varying polarizer 520 located in front of the linear polarizer 518. As discussed further below, the spatially varying polarizer 520 may provide variable retardation across its optical window, which enables the spatially varying polarizer to provide polarization compensation for the wire grid polarizer 522 of the optical system 502, which minimizes the variation in wavelength and angle of incidence of the wire grid polarizer. The spatially varying polarizer 520 may include a wave retarder formed of a birefringent material, such as a multi-twist retarder. Birefringence is a material property that has a refractive index that depends on the polarization and propagation direction of the light. The wave retarder changes the polarization state or phase of light propagating through the wave retarder. The wave retarder may have a slow axis (or extraordinary axis) and a fast axis (ordinary axis). When polarized light travels through the wave retarder, light along the fast axis travels faster than light along the slow axis.

[0058] The spatially varying polarizer 520 may be aligned so that its fast axis is aligned at 45 degrees with the transmission axis of the linear polarizer 518. The spatially varying polarizer 520 may be mounted in front of the linear polarizer 518 and optionally connected thereto.

[0059] The optical system 504 also includes a lens element including a lens portion 524 and a partially reflective mirror or surface 526. The lens portion 524 and the partially reflective mirror 526 can be formed as a single component or multiple components. The optical system 504 also includes a quarter wave plate 528 located between the lens portion 524 and the wire grid polarizer 522.

[0060] Although shown as planar for purposes of illustration, lens portion 524 or other components of display system 502 or optical system 504 may be non-planar (e.g., plano-convex, plano-concave, etc.) Furthermore, optical system 504 may include additional or fewer optical structures, such as refractive or diffractive lenses, partially reflective coatings, wave plates, reflective polarizers, linear polarizers, anti-reflective coatings, additional spatially varying polarizers, or other optical structures that allow light from display system 502 to be focused on the user's eye 510 with a desired optical power.

[0061] Reference now Figure 5 530-544 (arrows) are shown to describe a non-limiting example of how light travels through the display system 502 and the optical system 504 of the head mounted display system 500. Image light ray 530 may exit the pixel array 516 and pass through the linear polarizer 518 where it becomes linearly polarized in alignment with the transmission axis of the linear polarizer 518. In the example shown, the transmission axis of the linear polarizer 518 may be aligned with the transmission axis of the linear polarizer 518. Figure 5 X-axis alignment shown.

[0062] After passing through linear polarizer 518, light 530 passes through spatially varying polarizer 520 and becomes circularly polarized. Additional discussion of the operation of spatially varying polarizer 520 is provided elsewhere herein.

[0063] Circularly polarized light 530 from spatially varying polarizer 520 strikes partial reflector 526 and a portion of the light passes through the partial reflector as light 532. Light 532 is refracted or diffracted (partially focused) by the shape or properties of lens portion 524 of the lens element.

[0064] Light 532 is circularly polarized. Quarter wave plate 528 converts light 532 into linearly polarized light 534, where the linear polarization is Figure 5 Y-axis alignment.

[0065] Wire grid polarizer 522 may be located near or adjacent to quarter wave plate 528. Wire grid polarizer 522 may have orthogonal reflection and transmission (or pass) axes. Light polarized parallel to the reflection axis of wire grid polarizer 522 is reflected by the wire grid polarizer, and light polarized parallel to the transmission axis passes through wire grid polarizer 522. In the example shown, wire grid polarizer 522 may have a reflection axis aligned with the Y axis, so light ray 534 is reflected from the wire grid polarizer as reflected light ray 536.

[0066] The reflected light 536 has Figure 5 After passing through the quarter wave plate 528, the reflected light 536 becomes circularly polarized light 538. The circularly polarized light 538 passes through the lens portion 524, and a portion of the light 538 is reflected by the partial reflector 526 as reflected light 540. The portion of the light 538 that is transmitted by the partial reflector 526 as transmitted light 542 is converted from circularly polarized light to linearly polarized light by the spatially varying polarizer 520. The linearly polarized light has a linear polarization with respect to Figure 5 The Y-axis is shown aligned with the polarization so that light 542 is absorbed by linear polarizer 518.

[0067] As described above, reflected light 540 is circularly polarized. After returning through lens portion 524 and quarter wave plate 528, light 540 is linearly polarized into light 544, the polarization of which is aligned with the X-axis, which is parallel to the transmission axis of wire grid polarizer 522. Thus, light 544 passes through wire grid polarizer 522 to provide a visible image to the user's eye 510.

[0068] As described above, the spatially varying polarizer 520 can provide a phase delay that varies as a function of position (e.g., horizontal position, vertical position, radial position) over the field of view (e.g., on-axis to off-axis), which provides polarization compensation for the wavelength- and incident angle-sensitive wire grid polarizer 522. The specific manner in which the delay of the spatially varying polarizer 520 varies can depend on the specific structure and materials of the wire grid polarizer 520 or other components, such as the polarization state of the incident light, the incident angle, the materials, the geometry of the various components, etc.

[0069] Figure 6 A non-limiting exemplary plan view 600 of a spatially varying polarizer 520 is shown, showing its retardation pattern. In this example, the spatially varying polarizer 520 is configured to provide a circular wave or quarter wave (λ / 4) retardation at the center 602 of the optical window, and the retardation gradually (e.g., linearly, nonlinearly) decreases toward the periphery 604, where the spatially varying polarizer provides an elliptical wave or eighth wave (λ / 8) retardation. In general, the spatially varying polarizer 520 can provide a retardation that varies in any manner as a function of position, and the amount of retardation can be any value (e.g., λ / 20, λ / 10, λ / 8, λ / 4, λ, 2λ) used to provide polarization compensation for the wire grid polarizer 520. In addition, the amount of retardation can increase only in one or more directions, decrease only in one or more directions, or increase and decrease simultaneously. The amount of retardation can vary continuously or gradually, or can vary in multiple steps (e.g., two steps, 10 steps). The amount of delay may vary according to any type of function, including, for example, a linear function, a polynomial function, an exponential function, a step function, other types of functions, or combinations thereof.

[0070] As described above, in at least some embodiments, the spatially variable polarizer 520 can be formed of a multi-twisted retarder (MTR), which is a wave plate-like retardation film that provides precise and customized levels of broadband, narrowband, or multi-band retardation in a single film. More specifically, the MTR includes two or more twisted liquid crystal (LC) layers on a single substrate, and has a single alignment layer. Subsequent LC layers are directly aligned through the existing layers, allowing simple manufacturing, automatic layer alignment, and generating a monolithic film with a continuously varying optical axis.

[0071] In at least some embodiments, controller 514 is operably coupled to spatially varying polarizer 520 to selectively change the spatially dependent phase retardation of the spatially varying polarizer to any desired configuration. In other words, spatially varying polarizer 520 can be selectively switched. In such embodiments, one or more thin film transistor layers can be provided that allow controller 514 to selectively control the spatially dependent phase retardation of spatially varying polarizer 520 in any desired manner. Controller 514 can control the phase retardation at any desired rate, such as only once, periodically, at a rate equal to the frame rate of display system 502 or a fraction thereof, etc.

[0072] In at least some embodiments, the positions of quarter wave plate 528 and spatially varying polarizer 520 can be switched. In at least some embodiments, quarter wave plate 528 can be replaced with a spatially varying polarizer similar to or the same as spatially varying polarizer 520, such that optical system 504 includes two (or more) spatially varying polarizers.

[0073] By utilizing the spatially varying polarizers discussed herein, optical designers have significantly greater freedom to generate optical systems with improved performance and efficiency, which allows display systems to provide a better viewing experience, be less costly, be smaller in size or weight, consume less power, and provide other advantages that will be apparent to those skilled in the art.

[0074] The various embodiments described above may be combined to provide further embodiments. These and other changes may be made to the embodiments in light of the above detailed description. Generally, in the appended claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted as including all possible embodiments and the full range of equivalents granted by these claims. Therefore, the claims are not limited by the present disclosure.

Claims

1. Optical system, include: a lens element that receives light from the display subsystem; a first polarizer receiving light from the lens element; a quarter wave plate disposed between the lens element and the first polarizer; as well as A second polarizer is positioned between the display subsystem and the lens element, the second polarizer having a retardation that varies over an optical window of the second polarizer.

2. The optical system according to claim 1, in, The first polarizer includes a wire grid polarizer.

3. The optical system according to claim 1, in, The first polarizer comprises a wire grid polarizer and the second polarizer comprises a spatially varying polarizer.

4. The optical system according to claim 1, in, The second polarizer comprises a spatially varying polarizer.

5. The optical system according to claim 4, in, The spatially varying polarizer includes a multi-twist retarder.

6. The optical system according to claim 4, in, The spatially varying polarizer provides a quarter wave retardation at the center of the optical window and gradually decreases the retardation toward the periphery of the optical window.

7. The optical system according to claim 6, in, The spatially varying polarizer provides a one-eighth wave retardation at the periphery of the optical window.

8. The optical system according to claim 4, in, The spatially varying polarizer provides a first retardation at a center of the optical window and a second retardation at a periphery of the optical window, wherein the second retardation is less than the first retardation.

9. The optical system according to claim 4, in, The retardation of the spatially varying polarizer varies linearly or nonlinearly across the optical window.

10. The optical system according to claim 4, further comprising: include: A control circuit is operably coupled to the spatially varying polarizer, the control circuit being operative to selectively adjust the retardation provided by the spatially varying polarizer.

11. Optical system, include: a quarter wave plate, receiving light from the display subsystem; a lens element receiving light from the quarter wave plate; a first polarizer receiving light from the lens element; as well as A second polarizer is positioned between the lens element and the first polarizer, the second polarizer having a retardation that varies over an optical window of the second polarizer.

12. The optical system according to claim 11, in, The first polarizer comprises a wire grid polarizer.

13. The optical system according to claim 11, in, The first polarizer comprises a wire grid polarizer and the second polarizer comprises a spatially varying polarizer.

14. The optical system according to claim 11, in, The second polarizer comprises a spatially varying polarizer.

15. The optical system according to claim 14, in, The spatially varying polarizer includes a multi-twist retarder.

16. The optical system according to claim 14, in, The spatially varying polarizer provides a quarter wave retardation at the center of the optical window and gradually decreases the retardation toward the periphery of the optical window.

17. The optical system according to claim 16, in, The spatially varying polarizer provides a one-eighth wave retardation at the periphery of the optical window.

18. The optical system according to claim 14, in, The spatially varying polarizer provides a first retardation at a center of the optical window and a second retardation at a periphery of the optical window, wherein the second retardation is less than the first retardation.

19. The optical system according to claim 14, in, The retardation of the spatially varying polarizer varies linearly or nonlinearly across the optical window.

20. The optical system of claim 14, further comprising: include: A control circuit is operably coupled to the spatially varying polarizer, the control circuit being operative to selectively adjust the retardation provided by the spatially varying polarizer.

21. Head-mounted display system, include: A first near-eye display system and a second near-eye display system, each of the first near-eye display system and the second near-eye display system comprising: Optical subsystem, including: a lens element to receive light from the display; a first polarizer receiving light from the lens element; a quarter wave plate located between the lens element and the first polarizer; and a second polarizer, located between the display and the lens element, the The second polarizer has a retardation that varies over an optical window of the second polarizer.

22. The head mounted display system of claim 21, in, The first polarizer comprises a wire grid polarizer.

23. The head mounted display system of claim 21, in, The first polarizer comprises a wire grid polarizer and the second polarizer comprises a spatially varying polarizer.

24. The head mounted display system of claim 21, in, The second polarizer comprises a spatially varying polarizer.

25. The head mounted display system of claim 24, in, The spatially varying polarizer includes a multi-twist retarder.

26. The head mounted display system of claim 24, in, The spatially varying polarizer provides a quarter wave retardation at the center of the optical window and gradually decreases the retardation toward the periphery of the optical window.

27. The head mounted display system of claim 26, in, The spatially varying polarizer provides a one-eighth wave retardation at the periphery of the optical window.

28. The head mounted display system of claim 24, in, The spatially varying polarizer provides a first retardation at the center of the optical window and a second retardation at the periphery of the optical window.

29. The head mounted display system of claim 24, in, The retardation of the spatially varying polarizer varies linearly or nonlinearly across the optical window.

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