Optical system and head-mount display system

Abstract

To provide a method for increasing performance and efficiency of an optical system using an optical system, such as a head-mount display system.SOLUTION: An optical system may include a polarization reflection refraction optical system or "a pancake optical system" utilizing a wire grid polarizer as a reflection polarizer. The wire grid polarizer may not function uniformly regarding a wavelength or a varying incidence angle. For improving performance, a spatial variation polarizer is provided in the optical system so as to operate in order to bring polarization compensation to the wire grid polarizer, such that the wire grid polarizer functions more uniformly regarding a wavelength and / or an incidence angle (for example, on-axis and off-axis). The spatial variation polarizer is formed from a liquid crystal material, such as a multi-twist retarder.SELECTED DRAWING: Figure 5

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. Description of Related Art

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

[0003] The demand for improved display performance has increased with the development of smartphones, high-definition televisions, and other electronic devices. This demand has been further increased by the growing popularity of virtual reality and augmented reality systems, particularly those using HMDs. Virtual reality systems typically completely cover the wearer's eyes and substitute a "virtual" reality for the actual or physical field of view (or actual reality) in front of the wearer, while augmented reality systems typically provide a semi-transparent or transparent overlay of one or more screens in front of the wearer's eyes so that the actual field of view is augmented with additional information. Similarly, mediated reality systems can present information to the viewer that combines real-world elements with virtual elements.

[0004] However, such head-mounted displays, which reduce the distance between the viewer's eyes and the display and often have a poorly visible field of view, have increased display performance requirements in ways that conventional displays cannot meet (let alone do so cost-effectively). Microdisplays, such as OLED microdisplays, are much smaller than conventional displays, but present additional challenges. For example, microdisplays require lenses with very short focal lengths. Furthermore, the fixed size of the user's eye pupils reduces the f-number of lenses in HMDs that use microdisplays, which tends to increase aberrations in a given lens system. Furthermore, microdisplay pixels are small. The resulting increase in spatial resolution of the HMD optics further increases the challenges for designing and manufacturing lenses for such HMDs. Summary of the Invention

[0005] A head-mounted display system may be summarized as including a display subsystem operable to generate an image comprising linearly polarized light, and an 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 disposed between the lens element and the wire grid polarizer, and a spatially varying polarizer disposed between the display subsystem and the lens element, the spatially varying polarizer having a retardation characteristic 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 a gradually decreasing 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 a second retardation at the periphery of the optical window, the second retardation being smaller than the first retardation. The retardation of the spatially varying polarizer may vary linearly or non-linearly across the optical window.

[0007] The head mounted display system may further include a control circuit operably coupled to the spatially varying polarizer, the control circuit operable to selectively adjust the phase difference provided by the spatially varying polarizer.

[0008] A head-mounted display system may be summarized as including a display subsystem operable to generate an image including linearly polarized light, and an 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 disposed between the lens element and the wire grid polarizer, the spatially varying polarizer having a retardation characteristic 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 a gradually decreasing 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 a second retardation at the periphery of the optical window, the second retardation being smaller than the first retardation. The retardation of the spatially varying polarizer may vary linearly or non-linearly across the optical window.

[0010] The head mounted display system may further include a control circuit operably coupled to the spatially varying polarizer, the control circuit operable to selectively adjust the phase difference provided by the spatially varying polarizer.

[0011] A head-mounted display system may be summarized as including first and second near-to-eye display systems, each of the first and second near-to-eye display systems including a display subsystem operable to generate an image including linearly polarized light, and an optical subsystem, the optical subsystem 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 disposed between the lens element and the wire grid polarizer, and a spatially varying polarizer disposed between the display subsystem and the lens element, the spatially varying polarizer having a retardation characteristic that varies across 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, which may provide a quarter wave retardation at the center of the optical window and may gradually decrease the retardation towards the periphery of the optical window.

[0013] 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 a second retardation at the periphery of the optical window. The retardation of the spatially varying polarizer may vary linearly or non-linearly across the optical window. [Brief explanation of the drawings]

[0014] In the drawings, like elements or acts are identified with the same reference numerals. The sizes and relative positions of elements within the drawings are not necessarily drawn to scale. For example, the shapes and angles of various elements are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the legibility of the drawings. Furthermore, the particular shapes of the depicted elements are not necessarily intended to convey any information regarding the actual shape of the particular elements, but may merely be selected to facilitate recognition of the drawings.

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

[0016] [Figure 2] FIG. 1 illustrates an exemplary environment that employs at least some of the described techniques in conjunction with an exemplary head-mounted display device that is tethered to a video-rendering computing system and provides a virtual reality display to a user.

[0017] [Figure 3] 1 is a front pictorial view of an exemplary HMD device having a binocular display subsystem.

[0018] [Figure 4] FIG. 1 illustrates a top view of an HMD device having a binocular display subsystem and various sensors, according to an exemplary embodiment of the present disclosure.

[0019] [Figure 5] 1 is a cross-sectional view of an HMD device showing a display subsystem and its optics according to one non-limiting exemplary implementation.

[0020] [Figure 6] 6 is a plan view of an exemplary spatially varying polarizer of the optical system shown in FIG. 5, according to one non-limiting example implementation. DETAILED DESCRIPTION OF THE INVENTION

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

[0022] Unless the context otherwise requires, throughout this specification and the claims that follow, the word "comprising" is synonymous with "including" and is inclusive or open-ended (i.e., does not exclude additional, unrecited elements or method acts).

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

[0024] As used herein and in 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 used to include "and / or" unless the context clearly dictates otherwise.

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

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

[0027] An exemplary head-mounted display device application of the techniques described herein will be described first with reference to Figures 1-4. An exemplary implementation of a display system incorporating features of the present disclosure will then be described with reference to Figures 5 and 6. Exemplary Head-Mounted Display Systems and Environments

[0028] FIG. 1 is a schematic diagram of a networked environment 100 including a local media rendering (LMR) system 110 (e.g., a gaming console) that includes a local computing system 120 and a display device 180 (e.g., an HMD device with two display panels) suitable for performing at least some of the techniques described herein. In the illustrated embodiment of FIG. 1, the local computing system 120 is communicatively connected to the display device 180 via a transmission link 115 (the display device may be wired or tethered, such as via one or more cables (cable 220) as illustrated in FIG. 2, or alternatively may be wirelessly connected). In other embodiments, the local computing system 120 may provide encoded display image data via a wired or wireless link to a panel display device (e.g., a TV, console, or monitor), in addition to or instead of the HMD device 180, each of which includes one or more addressable pixel arrays. In various embodiments, the local computing system 120 may include a general-purpose computing system, a gaming console, a video stream processing device, a mobile computing device (e.g., a mobile phone, PDA, or other mobile device), a VR or AR processing device, or other computing system.

[0029] In the illustrated embodiment, local computing system 120 has components including one or more hardware processors (e.g., central 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, computer-readable storage 150, and a network connection 160. Also in the illustrated embodiment, an embodiment of an eye tracking subsystem 135 executes in memory 130 to perform at least some of the described techniques, such as using CPU 125 and / or GPU 144 to perform automated processing to implement these described techniques, and memory 130 may optionally also execute one or more other programs 133 (e.g., game programs that generate video or other images to be displayed). As part of an automated process implementing at least some of the techniques described herein, the eye tracking subsystem 135 and / or program 133 executing in memory 130 may store and retrieve various types of data, including that found in exemplary database data structures in storage 150; in this example, the data used may include various types of image data information found in database (“DB”) 154, various types of application data found in DB 152, various types of configuration data found in DB 157, and may include additional information such as system data or other information.

[0030] LMR system 110, in the illustrated embodiment, is also communicatively connected via one or more computer networks 101 and network links 102 to an exemplary network-accessible media content provider 190 that may further provide content to LMR system 110 for display, whether in addition to or instead of image generator 133. Media content provider 190 may include one or more computing systems (not shown), each of which may have components including one or more hardware processors, I / O components, local storage devices, and memory similar to those of local computing system 120, although for simplicity, some details of the network-accessible media content provider are not illustrated.

[0031] 1, it will be understood that in certain embodiments, some or all of the components of local media rendering system 110 may be integrated or housed within a single device, such as a portable gaming console, a portable VR entertainment system, an HMD device, etc. In such embodiments, transmission link 115 may include, for example, one or more system bus and / or video bus architectures.

[0032] As one example involving processing performed locally by local media rendering system 120, assume that local computing system is a gaming computing system in which application data 152 includes one or more gaming applications executed by CPU 125 using memory 130, and in which various video frame display data is generated and / or processed by image generation program 133, such as in conjunction with GPU 144 of video subsystem 140. To provide a high-quality gaming experience, large amounts of video frame data (corresponding to a high image resolution per video frame and a high "frame rate," approximately 60-180 of such video frames per second) are generated by local computing system 120 and provided to display device 180 via wired or wireless transmission link 115.

[0033] It will also be understood that computing system 120 and display device 180 are merely examples and are not intended to limit the scope of the present disclosure. Computing system 120 may instead include multiple computing systems or devices interacting with each other and may be connected to other devices not illustrated, such as through one or more networks such as the Internet, via the Web, or via a private network (e.g., a cellular network). More generally, computing systems or other computing nodes may include any combination of hardware or software capable of interacting with each other to perform the types of functions described, including, but not limited to, desktop or other computers, game consoles, database servers, network storage devices and other network devices, PDAs, mobile phones, wireless phones, pagers, electronic organizers, Internet appliances, television-based systems (e.g., using set-top boxes and / or personal / digital video recorders), and various other consumer products that include appropriate communications 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.

[0034] While various items are illustrated as being stored in and used in memory or storage, it will be understood that 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 one or more processors or other configured hardware circuits or hardware including memory or storage (e.g., by executing software instructions of one or more software programs and / or by storing such software instructions and / or data structures), such as when configured by one or more software programs 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, such as a hard disk or flash drive or other non-volatile storage device, volatile or non-volatile memory (e.g., RAM), network storage device, or portable media article (e.g., DVD disk, CD disk, optical disk, etc.) read by an appropriate drive or via an appropriate connection. The systems, components, and data structures may also, in some embodiments, be transmitted over various computer-readable transmission media, including wireless-based media and wire / cable-based media, as a generated data signal (e.g., as part of a carrier wave or other analog or digital propagated signal), and may take various forms (e.g., as part of one or multiplexed analog signals, or as multiple individual digital packets or frames). Such computer program products may take other forms in other embodiments. Accordingly, the invention may be practiced using other computer system configurations.

[0035] 2 illustrates an example environment 200 that provides a virtual reality display to a human user 206 using at least some of the described techniques, with an example HMD device 202 coupled via a tethered connection 220 (or a wireless connection in other embodiments) to a video rendering computing system 204. The user wears the HMD device 202 and receives display information of a simulated environment that differs from the actual physical environment from the computing system 204 via the HMD device, with the computing system acting as an image rendering system that provides images of the simulated environment (e.g., images generated by game programs and / or other software programs running on the computing system) to the HMD device for display to the user. In this example, the user can further move around within a tracked volume 201 of the actual physical environment 200 and may further have one or more I / O (“input / output”) devices (including handheld controllers 208 and 210 in this example) that enable the user to further interact with the simulated environment.

[0036] In the illustrated example, the environment 200 may include one or more base stations 214 (two are shown labeled base stations 214a and 214b) that may facilitate tracking of the HMD device 202 or the controllers 208 and 210. The position of the HMD device is tracked, such as to enable a corresponding portion of the simulated environment to be displayed to the user wearing the HMD device as the user moves from place to place or turns the HMD device 202, and the controllers 208 and 210 may further use similar techniques for use in tracking the position of the controller (and optionally, for use in using the information to help determine or confirm the position of the HMD device). After the tracked position of the HMD device 202 is known, the corresponding information is transmitted to the computing system 204 via a tether 220 or wirelessly. The computing system uses the tracked position information to generate one or more subsequent images of the simulated environment to display to the user.

[0037] There are many different methods of position tracking that may be used in various implementations of the present disclosure, including, but not limited to, acoustic tracking, inertial tracking, magnetic tracking, optical tracking, combinations thereof, and the like.

[0038] In at least some implementations, the HMD device 202 may include one or more optical receivers or sensors that can be used to implement tracking functionality or other aspects of the present disclosure. For example, each base station 214 may sweep an optical signal throughout the tracked volume 201. Depending on the requirements of each particular implementation, each base station 214 may generate more than one optical signal. For example, while one base station 214 is typically sufficient for six-degrees-of-freedom tracking, multiple base stations (e.g., base stations 214a, 214b) may be necessary or desirable in some embodiments to provide stable, room-scale tracking for the HMD device and peripherals. In this example, optical receivers are integrated into the HMD device 202 and / or other tracked objects (such as controllers 208 and 210). In at least some implementations, optical receivers may be combined with accelerometer and gyroscope inertial measurement units (“IMUs”) on each tracked device to support low-latency sensor fusion.

[0039] In at least some implementations, each base station 214 includes two rotors that sweep a line beam along a vertical axis throughout the tracked volume 201. At the beginning of each sweep cycle, the base station 214 may emit an omnidirectional light pulse (called a "synchronization signal") that is visible to all sensors attached to the tracked object. Each sensor then calculates its own angular position in the swept volume by timing the duration between the synchronization signal and the beam signal. Sensor distance and orientation may be determined using multiple sensors attached to a single fixed object.

[0040] One or more sensors located on the tracked object (e.g., HMD device 202, controllers 208 and 210) may include optoelectronic devices capable of detecting modulated light from the rotor. For visible or near-infrared (NIR) light, silicon photodiodes and suitable amplifier / detector circuitry may be used. Because the environment 200 may contain static and time-varying signals (optical noise) having wavelengths similar to those of the base station 214 signal, in at least some implementations, the light of the base station may be modulated in a manner that facilitates differentiation from any interfering signals and / or facilitates screening the sensor from any emission wavelengths other than that of the base station signal.

[0041] 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 that it uses the position of a camera or other sensor to determine the position of the HMD. In inside-out tracking, the camera or sensor is located on the HMD or the object being tracked, while in outside-out tracking, the camera or sensor is placed in a fixed position in the environment.

[0042] An HMD using inside-out tracking uses one or more "outside-looking" cameras to determine how its position is changing relative to the environment. As the HMD moves, the sensors recalibrate its position in the room, and the virtual environment responds accordingly in real time. This type of positional tracking can be achieved with or without markers placed in the environment. Cameras placed on the HMD observe features of the surrounding environment. If markers are used, they are designed to be easily detected by the tracking system and placed in specific areas. In "markerless" inside-out tracking, the HMD system uses salient features already present in the environment (e.g., terrain) to determine position and orientation. The HMD system's algorithms identify 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 improve the accuracy of positional tracking.

[0043] FIG. 3 shows information 300 illustrating 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 structure 343 that supports a front or forward-facing camera 346 and one or more types of multiple sensors 348a-348d (collectively 348). As one example, some or all of the sensors 348, such as optical sensors that detect and use optical information emitted from one or more external devices (e.g., base station 214 of FIG. 2, not shown), can help determine the location and orientation of the device 344 in space. As shown, the forward-facing camera 346 and sensors 348 are pointed forward toward a real-world scene or environment (not shown) in which the user 342 operates the HMD device 344. The real-world 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 fewer or more than the number of sensors shown. The HMD device 344 may further include one or more additional components not attached to the front structure (e.g., internal to the HMD device), such as an IMU (Inertial Measurement Unit) electronic device 347 that measures and reports certain forces, angular velocities, and / or magnetic fields surrounding the HMD device 344 (e.g., using a combination of accelerometers and gyroscopes, and optionally magnetometers). The HMD device may further include additional components not shown, including one or more display panels and optical lens systems that face the user's eyes (not shown), and optionally have one or more associated built-in motors for changing the alignment or other positioning of one or both of the optical lens systems and / or display panels within the HMD device, as described in more detail below with respect to FIG. 4.

[0044] The illustrated example HMD device 344 is supported on the head of a user 342 based at least in part on one or more straps 345 attached to the housing of the HMD device 344 and extending wholly or partially around the user's head. Although not illustrated here, the HMD device 344 may further include one or more external motors, such as those attached to one or more of the straps 345, and automatic correction operations may involve adjusting such straps using such motors to correct alignment or other positioning of the HMD device on the user's head. It will be understood that the HMD device may include other support structures (e.g., nose pads, chin straps, etc.) not illustrated here, in addition to or instead of the illustrated straps, and some embodiments may include one or more such other support structures with attached motors that may similarly adjust their shape and / or position to correct alignment or other positioning of the HMD device on the user's head. Other display devices not attached to the user's head may similarly be attached to or part of one or more structures that affect the positioning of the display device, and such other devices, at least in some embodiments, may include motors or other mechanical actuators that similarly modify their shape and / or position to modify the alignment or other positioning of the display device relative to one or more pupils of one or more users of the display device.

[0045] 4 illustrates a simplified plan view 400 of an HMD device 405 including a pair of near-to-eye display systems 402 and 404. The HMD device 405 may be the same as or similar to the HMD devices illustrated in FIGS. 1-3, for example, or may be a different HMD device, and the HMD devices described herein may be used in examples further described below. The near-to-eye display systems 402 and 404 of FIG. 4 include display panels 406 and 408, respectively (e.g., OLED microdisplays, LCD displays), and respective optical lens systems 410 and 412, each having one or more optical lenses. The display systems 402 and 404 may be mounted or otherwise disposed within a housing (or frame) 414, which includes a front portion 416 (e.g., the same as or similar to front surface 343 of FIG. 3 ), a left temple 418, a right temple 420, and an inner surface 421 that contacts or is adjacent to a wearer's face when a user 424 wears the HMD device. The two display systems 402 and 404, which may be worn on a head 422 of a wearer user 424, may be secured to the housing 414 in an eyeglass configuration, with the left temple 418 and right temple 420 positioned over the user's ears 426 and 428, respectively, and a nose pad 492 positioned over the user's nose 430. In the example of Figure 4, the HMD device 405 may be partially or completely supported on the user's head by nose pads and / or over-ear temples, although in some embodiments, a strap (not shown) or other structure may be used to secure the HMD device to the user's head, as in the embodiments shown in Figures 2 and 3. The housing 414 may be shaped and sized 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, such that the target position of each pupil 494 is centered both vertically and horizontally in front of the respective optical lens system and / or display panel.For purposes of explanation, housing 414 is shown in a simplified manner similar to eyeglasses, but it should be understood that in practice more elaborate structures (e.g., goggles, integrated headbands, helmets, straps, etc.) may be used to support and position display systems 402 and 404 on head 422 of user 424.

[0046] The HMD device 405 of FIG. 4 , and other HMD devices described herein, can present a virtual reality display to a user, such as via a corresponding video presented at a display rate such as 30, 60, or 90 frames (or images) per second, and in other embodiments of similar systems, an augmented reality display may be presented to a user. The displays 406 and 408 of FIG. 4 may each generate light that is channeled through respective optical lens systems 410 and 412 and then focused by the optical lens systems onto the eyes 432 and 434, respectively, of the user 424. The pupil 494 opening of each eye, through which light enters the eye, typically ranges in size from 2 mm (millimeters) in diameter in very bright conditions to as much as 8 mm in low light conditions, with the larger iris containing the pupil being approximately 12 mm in size. The pupil (and surrounding iris) can also typically move several millimeters laterally and / or vertically within the visible portion of the eye with the eyelids open, which also causes the pupil to move to different depths from the display's optical lenses or other physical elements for different horizontal and vertical positions as the eyeball pivots about its center (resulting in a three-dimensional volume through which the pupil can move). Light entering the user's pupil is viewed by the user 424 as an image and / or video. In some implementations, the distance between each of the optical lens systems 410 and 412 and the user's eyes 432 and 434 may be relatively short (e.g., less than 30 mm, less than 20 mm), which advantageously allows the HMD device to feel lighter to the user because the weight of the optical lens systems and display system is relatively close to the user's face and may also provide the user with a larger field of view. Although not illustrated here, some embodiments of such HMD devices may include various additional built-in and / or external sensors.

[0047] In the illustrated embodiment, the HMD device 405 of FIG. 4 further includes hardware sensors and additional components, such as to include one or more accelerometers and / or gyroscopes 490 (e.g., as part of one or more IMU units). As described in more detail elsewhere herein, values ​​from the accelerometers and / or gyroscopes may be used to locally determine the orientation of the HMD device. Additionally, the HMD device 405 may include one or more front-facing cameras, e.g., a camera 485 on the exterior surface of the front portion 416, the information of which may be used as part of the HMD device's computation, such as to provide AR or positioning functionality. Additionally, the HMD device 405 may further include other components 475 (e.g., electronic circuitry controlling the display of images on the display panels 406 and 408, internal storage, one or more batteries, a position tracking device that interacts with an external base station, etc.), which are described in more detail elsewhere herein. Other embodiments may not include one or more of components 475, 485, and / or 490. Although not illustrated here, some embodiments of such HMD devices may include various additional built-in and / or external sensors, such as for tracking various other types of movements and positions of the user's body, eyes, controllers, etc.

[0048] In the illustrated embodiment, the HMD device 405 of FIG. 4 further includes hardware sensors and additional components that may be used by the disclosed embodiments as part of the described techniques to determine the direction of the user's pupils or gaze, and that may be provided to one or more components associated with the HMD device for use by such components, as described elsewhere herein. The hardware sensors in this example include one or more eye tracking assemblies 472 of an eye tracking subsystem mounted on or near the display panels 406 and 408 and / or located on the inner surface 421 near the optical lens systems 410 and 412, for use in obtaining information regarding the actual positions of the user's pupils 494, e.g., separately for each pupil in this example.

[0049] Each of the eye tracking assemblies 472 may include one or more light sources (e.g., IR LEDs) and one or more photodetectors (e.g., silicon photodiodes). Additionally, while for clarity, only a total of four eye tracking assemblies 472 are shown in FIG. 4 , it should be understood that in practice a different number of eye tracking assemblies may be provided. In some embodiments, a total of eight eye tracking assemblies 472 are provided, i.e., four eye tracking assemblies for each eye of the user 424. Furthermore, in at least some implementations, each eye tracking assembly includes a light source directed toward one of the eyes 432 and 434 of the user 424, a photodetector positioned to receive light reflected by the respective eye of the user, and a polarizer positioned and configured to prevent light reflected by specular reflection from reaching the photodetector.

[0050] As described in more detail elsewhere herein, information from the eye tracking assembly 472 may be used to determine and track a user's gaze direction when using the HMD device 405. Additionally, in at least some embodiments, the HMD device 405 may include one or more internal motors 438 (or other movement mechanisms) that may be used to move (439) the alignment and / or other positioning (e.g., vertically, horizontally left-right, and / or horizontally front-to-back) of the optical lens systems 410 and 412 and / or the display panels 406 and 408 within the housing of the HMD device 405, such as to personalize or otherwise adjust a target pupil position of one or both of the near-to-eye display systems 402 and 404 that corresponds to the actual position of one or both of the pupils 494. Such motors 438 may be controlled, for example, by user manipulation of one or more control buttons 437 on the housing 414 and / or by user manipulation of one or more associated separate I / O controllers (not shown). In other embodiments, HMD device 405 may control the alignment and / or other positioning of optical lens systems 410 and 412 and / or display panels 406 and 408 without using such motors 438, for example, using adjustable positioning mechanisms (e.g., screws, sliders, ratchets, etc.) that are manually changed by a user using control buttons 437. Additionally, while motor 438 is illustrated in FIG. 4 for only one of the near-to-eye display systems, in some embodiments each near-to-eye display system may have its own motor or motors, and in some embodiments one or more motors may be used to control each of multiple near-to-eye display systems (e.g., independently).

[0051] While the described techniques may be used in some embodiments with display systems similar to those illustrated, in other embodiments, other types of display systems may be used, including, for example, those having one optical lens and display device, or those having multiple such optical lenses and display devices. Non-exclusive examples of other such devices include cameras, telescopes, microscopes, binoculars, spotting scopes, survey scopes, and the like. Furthermore, the described techniques may be used with a wide variety of display panels or other display devices that emit light to form images, which are viewed by one or more users through one or more optical lenses, as described elsewhere herein. In other embodiments, a user may view one or more images through one or more optical lenses, such as those generated in a manner other than a display panel, such as on a surface that partially or wholly reflects light from another light source (e.g., a laser scanning beam). [Exemplary Display System]

[0052] FIG. 5 is a cross-sectional side view of a head-mounted display system 500 including a display system 502 and optical system 504 supported by a support structure 506 (such as a housing, helmet, goggles, eyeglasses, or other headwear). The support structure 506 supports the display system 502 and optical system 504 in front of a user's eyes (e.g., eyes 510) when the user views the system in a Z-axis direction indicated by arrow 512 shown in FIG. 5. A control circuit 514 may optionally be coupled to the optical system 504 or one or more components of the display system 502, as described elsewhere herein. By way of example, the display system 502 and optical system 504 may be similar to or identical to the display system and optical system described above with reference to FIG. 4. The display system 502 and optical system 504 may be operable to display an image to the user 510. As described further below, the optical system 504 may utilize catadioptric or "pancake" optics to provide an image from the display system 502 to the user's eye 510. The spacing and size of the components of head mounted display system 400 may vary from that illustrated. As an example, components shown as being spaced apart may be positioned adjacent to one another in various orders, etc.

[0053] The display system 502 includes an image source such as a pixel array 516. The pixel array 516 may include a two-dimensional array of pixels that emit light. By way of non-limiting example, the 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.

[0054] A linear polarizer 518 may be positioned in front of the pixel array 516 to provide polarized light from the pixel array 516. In at least some implementations, the pixel array 516 may generate linearly polarized light by designing it such that the linear polarizer 518 may be omitted. As an example, the linear polarizer 518 may have a transmission or pass axis aligned with the X-axis shown in FIG. 5.

[0055] The optical system 504 may include a spatially varying polarizer 520 positioned in front of the linear polarizer 518. As described further below, the spatially varying polarizer 520 can provide a retardation characteristic that varies across its optical window, allowing the spatially varying polarizer to provide polarization compensation to the wire grid polarizer 522 of the optical system 502, thereby minimizing the variation with wavelength and angle of incidence of the wire grid polarizer. The spatially varying polarizer 520 may include a wavelength retarder formed of a birefringent material, such as a multi-twist retarder. Birefringence is a property of a material in which the refractive index depends on the polarization and propagation direction of the light. The wavelength retarder changes the polarization state or phase of light traveling through it. The wavelength retarder may have a slow axis (or extraordinary axis) and a fast axis (or ordinary axis). When polarized light travels through the wavelength retarder, light along the fast axis travels faster than light along the slow axis.

[0056] The spatially varying polarizer 520 may be aligned so that its fast axis is aligned at 45° to the transmission axis of the linear polarizer 518. The spatially varying polarizer 520 may be placed in front of the linear polarizer 518 and may optionally be attached to the linear polarizer.

[0057] The optical system 504 further 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 may be formed as a single component or multiple components. The optical system 504 further includes a quarter-wave plate 528 disposed between the lens portion 524 and the wire grid polarizer 522.

[0058] While the lens portion 524 or other components of the display system 502 or optical system 504 are shown as planar for illustrative purposes, they may be non-planar (e.g., plano-convex, plano-concave, etc.). Additionally, the optical system 504 may include additional or fewer optical structures, such as refractive or diffractive lenses, partially reflective films, wave plates, reflective polarizers, linear polarizers, anti-reflective films, additional spatially varying polarizers, or other optical structures that enable light rays from the display system 502 to be focused at the user's eye 510 at a desired light intensity.

[0059] A non-limiting example of how light may pass through the display system 502 and optical system 504 of the head mounted display system 500 will now be described with reference to light rays 530-544 (arrows) shown in Figure 5. Image light ray 530 may exit the pixel array 516 and pass through the linear polarizer 518, becoming linearly polarized light aligned with the transmission axis of the linear polarizer 518. In the illustrated example, the transmission axis of the linear polarizer 518 may be aligned with the X-axis shown in Figure 5.

[0060] After passing through linear polarizer 518, light ray 530 passes through spatially varying polarizer 520 and becomes circularly polarized. Further explanation of the operation of spatially varying polarizer 520 is provided elsewhere herein.

[0061] Circularly polarized light 530 from spatially varying polarizer 520 strikes partially reflecting mirror 526, and a portion of the light ray passes through the partially reflecting mirror as light ray 532. Light ray 532 is refracted or diffracted (partially focused) by the shape or properties of lens portion 524 of the lens element.

[0062] Light ray 532 is circularly polarized. Quarter wave plate 528 converts light ray 532 into linearly polarized light ray 534, with the linear polarization aligned with the Y-axis in FIG.

[0063] Wire grid polarizer 522 may be positioned proximate 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 illustrated example, wire grid polarizer 522 may have a reflection axis aligned with the Y-axis, such that light ray 534 reflects from the wire grid polarizer as reflected light ray 536.

[0064] Reflected ray 536 has linear polarization aligned with the Y-axis shown in Figure 5. After passing through quarter-wave plate 528, reflected ray 536 becomes circularly polarized ray 538. Circularly polarized ray 538 passes through lens assembly 524, and a portion of ray 538 is reflected by partially reflecting mirror 526 as reflected ray 540. The portion of ray 538 that is transmitted through partially reflecting mirror 526 as transmitted ray 542 is converted from circularly polarized to linearly polarized light by space-varying polarizer 520. Because linearly polarized light has polarization aligned with the Y-axis shown in Figure 5, ray 542 is absorbed by linear polarizer 518.

[0065] As mentioned above, reflected light ray 540 is circularly polarized. After passing through lens portion 524 and quarter-wave plate 528 again, light ray 540 becomes linearly polarized as light ray 544 whose polarization is aligned with the X-axis, which is parallel to the transmission axis of wire grid polarizer 522. Light ray 544 therefore passes through wire grid polarizer 522 and provides a viewable image to user's eye 510.

[0066] As described above, the spatially varying polarizer 520 that provides polarization compensation to the wire grid polarizer 522 may provide a phase retardation that varies with position (e.g., lateral position, vertical position, radial position) across the field of view (e.g., on-axis to off-axis), which is sensitive to wavelength and angle of incidence. The particular manner in which the retardation of the spatially varying polarizer 520 varies may depend on the particular configuration and materials of the wire grid polarizer 520 or other components, such as the polarization state of the incident light, the angle of incidence, the materials, the geometry of the various components, etc.

[0067] 6 shows a non-limiting, exemplary plan view 600 of a spatially varying polarizer 520, illustrating the phase difference pattern of the spatially varying polarizer. In this example, the spatially varying polarizer 520 is configured to provide a circular or quarter-wave (λ / 4) phase difference at the center 602 of the optical window, which gradually decreases (e.g., linearly or non-linearly) toward the periphery 604, where the spatially varying polarizer provides an elliptical or eighth-wave (λ / 8) phase difference. In general, the spatially varying polarizer 520 may provide a position-varying phase difference in any manner, and the amount of phase difference may be any value (e.g., λ / 20, λ / 10, λ / 8, λ / 4, λ, 2λ) operable to provide polarization compensation for the wire grid polarizer 520. Furthermore, the amount of phase difference may increase in only one or more directions, decrease in only one or more directions, or both increase and decrease. The amount of phase difference may vary continuously or gradually, or may vary in multiple steps (e.g., 2 steps, 10 steps), etc. The amount of phase difference 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.

[0068] As mentioned above, in at least some implementations, the spatially varying polarizer 520 may be formed from a multi-twist retarder (MTR), which is a waveplate-like retarder film that provides precise and customized levels of broadband, narrowband, or multiband retardation in a single thin film. More specifically, an MTR has two or more twisted liquid crystal (LC) layers on a single substrate along with an alignment layer. The next LC layer is directly aligned with the previous layer, enabling simple fabrication, automatic inter-layer alignment, and a monolithic film with a continuously varying optical axis.

[0069] In at least some implementations, the controller 514 may be operatively coupled to the spatially varying polarizer 520 to selectively alter the spatially dependent phase retardation of the spatially varying polarizer to any desired configuration. In other words, the spatially varying polarizer 520 may be selectively switchable. In such implementations, one or more thin film transistor layers may be provided that allow the spatially dependent phase retardation of the spatially varying polarizer 520 to be selectively controlled in any desired manner by the controller 514. The controller 514 may control the phase retardation at any desired frequency, such as once, periodically, at a frequency equal to or a fraction of the frame rate of the display system 502, etc.

[0070] In at least some implementations, the positions of the quarter-wave plate 528 and the spatially varying polarizer 520 may be swapped. In at least some implementations, the quarter-wave plate 528 may be replaced with a spatially varying polarizer similar to or identical to the spatially varying polarizer 520, such that the optical system 504 includes two (or more) spatially varying polarizers.

[0071] By utilizing the spatially varying polarizers described herein, optical designers have significantly more freedom to create optical systems with improved performance and efficiency, thereby enabling display systems that provide a better viewing experience, are less costly, smaller in size or weight, consume less power, and offer other advantages that will be apparent to those skilled in the art.

[0072] The various implementations described above may be combined to provide further implementations. These and other changes can be made to each implementation in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific implementations disclosed in the specification and claims, but should be construed to include all possible implementations along with the full range of equivalents to which such claims are entitled. Accordingly, the claims are not limited by this disclosure.

Claims

1. a lens element that receives light from the display subsystem; a first polarizer that receives light from the lens element; a quarter wave plate disposed between the lens element and the first polarizer; a second polarizer disposed between the display subsystem and the lens element, the second polarizer having a retardation characteristic that varies across an optical window of the second polarizer; An optical system comprising:

2. The optical system of claim 1 , wherein the first polarizer comprises a wire grid polarizer.

3. The optical system of claim 1 , wherein the first polarizer comprises a wire grid polarizer and the second polarizer comprises a spatially varying polarizer.

4. The optical system of claim 1 , wherein the second polarizer comprises a spatially varying polarizer.

5. The optical system of claim 4 , wherein the spatially varying polarizer comprises a multi-twist retarder.

6. The optical system of claim 4 , wherein the spatially varying polarizer provides a quarter-wave retardation at the center of the optical window and gradually reduces the wavelength retardation toward the periphery of the optical window.

7. The optical system of claim 6 , wherein the spatially varying polarizer provides an eighth wave retardation at the periphery of the optical window.

8. 5. The optical system of claim 4, wherein the spatially varying polarizer provides a first phase difference at a center of the optical window and a second phase difference at a periphery of the optical window, the second phase difference being less than the first phase difference.

9. The optical system of claim 4 , wherein the phase difference of the spatially varying polarizer varies linearly or non-linearly across the optical window.

10. The optical system of claim 4 , further comprising a control circuit operably coupled to the spatially varying polarizer, the control circuit operable to selectively adjust the phase difference provided by the spatially varying polarizer.

11. An optical system comprising: a quarter wave plate that receives light from the display subsystem; a lens element that receives light from the quarter wave plate; a first polarizer that receives light from the lens element; a second polarizer disposed between the lens element and the first polarizer, the second polarizer having a retardation characteristic that varies across an optical window of the second polarizer; An optical system comprising:

12. The optical system of claim 11 , wherein the first polarizer comprises a wire grid polarizer.

13. The optical system of claim 11 , wherein the first polarizer comprises a wire grid polarizer and the second polarizer comprises a spatially varying polarizer.

14. The optical system of claim 11 , wherein the second polarizer comprises a spatially varying polarizer.

15. The optical system of claim 14 , wherein the spatially varying polarizer comprises a multi-twist retarder.

16. 15. The optical system of claim 14, wherein the spatially varying polarizer provides a quarter wave retardation at the center of the optical window and gradually reduces the wavelength retardation towards the periphery of the optical window.

17. The optical system of claim 16 , wherein the spatially varying polarizer provides an eighth wave retardation at the periphery of the optical window.

18. 15. The optical system of claim 14, wherein the spatially varying polarizer provides a first phase difference at a center of the optical window and a second phase difference at a periphery of the optical window, the second phase difference being less than the first phase difference.

19. The optical system of claim 14 , wherein the phase difference of the spatially varying polarizer varies linearly or non-linearly across the optical window.

20. 15. The optical system of claim 14, further comprising a control circuit operably coupled to the spatially varying polarizer, the control circuit operable to selectively adjust the phase difference provided by the spatially varying polarizer.

21. 1. A head mounted display system comprising first and second near-to-eye display systems, each of the first and second near-to-eye display systems; an optical subsystem; the optical subsystem: a lens element that receives light from the display; a first polarizer that receives light from the lens element; a quarter wave plate disposed between the lens element and the first polarizer; a second polarizer disposed between the display and the lens element, the second polarizer having a retardation characteristic that varies across an optical window of the second polarizer; A head-mounted display system.

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

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

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

25. 25. The head mounted display system of claim 24, wherein the spatially varying polarizer comprises a multi-twist retarder.

26. 25. The head mounted display system of claim 24, wherein the spatially varying polarizer provides a quarter wave retardation at the center of the optical window and gradually reduces the wavelength retardation towards the periphery of the optical window.

27. 27. The head mounted display system of claim 26, wherein the spatially varying polarizer provides an eighth wave retardation at the periphery of the optical window.

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

29. 25. The head mounted display system of claim 24, wherein the retardation of the spatially varying polarizer varies linearly or non-linearly across the optical window.

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