Patent Publication Number: US-11044402-B1

Title: Power management for optical position tracking devices

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and claims priority to, U.S. patent application Ser. No. 15/984,130, filed May 18, 2018, of the same title, which is incorporated herein by reference as if fully set forth below. 
    
    
     BACKGROUND 
     Virtual reality (VR) systems allow a user to become immersed in a virtual environment by displaying the virtual environment, sensing the position and movement of the user, and responding to the position and movement of the user. VR games often rely on wearable devices or other devices that sense natural movements of the user. For example, rather than operating a joystick to throw punches in a boxing game, the boxing game may receive input regarding the actual positions and movements of a user&#39;s hands, so that the user is able play the game by actually punching with their arms and hands. Similarly, a virtual reality system may allow a user to move through a displayed virtual environment by taking physical steps, to grasp objects, to press virtual buttons, and so forth. 
     In some systems, a user may wear or hold what are referred to as VR controllers. A VR controller is a device that provides output such as audio and video to a user. For example, a user may wear a VR headset that displays the virtual environment to the user. A VR controller may also accept or detect user input, allowing the user to interact with or move relative to elements of the virtual environment. Specifically, some VR controllers detect user positions and movements. 
     The position and movement of a user may be detected in various ways. In some systems, optical techniques are used to detect user movement. In particular, some systems may use light sensors, positioned on wearable or handheld devices such as VR headsets or VR hand controllers, to detect optical signals that convey position information. 
     A VR controller typically operates wirelessly, using rechargeable batteries for power. The useable time of the VR controller is therefore limited by the available battery capacity. Accordingly, it is important to minimize or limit the power consumption of VR controllers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical components or features. 
         FIG. 1  is a diagram showing a space within which a virtual reality (VR) system operates. 
         FIG. 2  is a diagram of an example VR headset. 
         FIG. 3  is a diagram of an example VR hand controller; 
         FIG. 4  is a timing diagram showing optical signals emitted by a stationary emitter and corresponding optical signals received by a VR controller in one embodiment. 
         FIG. 5  is a timing diagram showing optical signals emitted by a stationary emitter and corresponding optical signals received by a VR controller in another embodiment. 
         FIG. 6  is a timing diagram showing optical signals emitted by a stationary emitter and corresponding optical signals received by a VR controller in yet another embodiment. 
         FIG. 7  is a flow diagram illustrating an example method of disabling light sensors to reduce power consumption of a VR controller. 
         FIGS. 8A, 8B, 8C, and 8D  are flow diagrams illustrating further details of disabling sensors to reduce power consumption of a VR controller. 
         FIG. 9  is a flow diagram illustrating yet further details of disabling sensors in an alternative embodiment. 
         FIG. 10  is a block diagram of a VR controller that may embody the methods and techniques described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Described herein, among other things, are techniques for detecting the three-dimensional position and pose of an object, as well as devices and systems for implementing techniques for position and pose detection. 
     In accordance with embodiments disclosed herein, an optical emitter is mounted at a stationary position within a room or other space. The optical emitter is configured to scan a laser line through the room to convey positional information to a position tracking device within the room. For example, the scanning of the laser line may be controlled so that the angle at which the laser line is projecting at any instant is a function of the elapsed time after a synchronization pulse. As another example, the laser line may be modulated or otherwise encoded to convey its current instantaneous projection angle as the laser line scans over or through a space. 
     In the described embodiments, a virtual reality (VR) controller or other moveable or wearable position tracking device has light sensors arranged to receive optical signals from one or more stationary optical emitters as described above. Specifically, an individual light sensor may detect a laser line at the moment that the laser line crosses the light sensor. Information regarding the laser line is then analyzed to determine a position coordinate of the VR controller. For example, the VR controller may measure the time difference between receiving an optical synchronization pulse and subsequently detecting a scanning laser line, and the projection angle of the laser line at the moment that the laser line was detected by the VR controller can then be calculated as a function of this time difference. As another example, the VR controller may demodulate or decode the received laser line signal to obtain an angular coordinate value embedded in the laser line signal, where the angular coordinate corresponds to the projected angle of the laser line at the moment that the laser line was detected by the VR controller. 
     At any given time, any number of the light sensors may be positioned and oriented so that they can receive and detect a laser line projected from a particular stationary emitter. The VR controller and/or supporting computing devices use the angular position information obtained by analyzing signals from multiple light sensors and multiple stationary emitters to determine a three-dimensional position and pose of the VR controller. 
     A single emitter, at a single location, may be configured to generate laser lines that are scanned in multiple respective directions, such as along horizontal and vertical axes, so that a VR controller can determine both horizontal and vertical angular coordinates relative to the emitting device. The lasers are scanned in what are referred to as emitter cycles, where the optical signals of each emitter cycle indicate current or new positional information. 
     In order to reduce power consumption by the light sensors, some light sensors can be disabled in certain situations where these light sensors are unlikely to be able to detect upcoming laser lines. For example, individual sensors may not be facing a particular emitter or may be blocked from receiving signals from the emitter. The VR controller is configured to determine which of its sensors did not detect the laser lines of a particular emitter cycle, and to disable these sensors during one or more subsequent emitter cycles. In some cases, sensors such as this may be disabled only if the VR controller is not moving. In some cases, sensors may be disabled because the input from those sensors is extraneous to a particular application or duplicative of input from other sensors. In some cases, the number of subsequent emitter cycles during which a sensor is disabled may vary depending on the speed at which the VR controller is moving. In some cases, the VR controller may not disable a particular sensor if the sensor is near another sensor that did detect a scanning laser line during the previous emitter cycle. In some cases, the sensor may be disabled for most of an emitter cycle, but enabled during a time span within which the laser line is expected to cross and impinge upon the VR controller. These and other details will be explained in more detail in the following discussion. 
       FIG. 1  illustrates the use of virtual reality (VR) controllers in an example embodiment. Specifically,  FIG. 1  shows a physical space  102 , which in this example is a room, and a user  104  within the space  102 . The user  104  is wearing a VR headset  106  and a pair of VR hand controllers  108 . The VR headset  106  and the VR hand controllers  108  are examples of wearable components that are referred to as VR controllers or VR motion controllers, and more generally as moveable position tracking devices. 
     The VR headset  106  has an internal display (not shown) that presents a simulated view of a virtual environment. For example, the simulated view may show a room or other space, and may also show objects within the virtual space. As the user  104  moves, the VR headset  106  senses the movement and the simulated view changes to reflect the new position or orientation of the user  104  within the virtual space. By turning their head, for example, the user  104  may look in different directions and/or at different objects within the virtual environment. 
     The VR hand controllers  108  similarly sense movements of the hands of the user  104 . The virtual environment displayed by the VR headset  106  may include simulated hands that move in accordance with the movement of the user&#39;s actual hands. In some embodiments, the VR hand controllers  108  may also sense finger movements, allowing the user  104  to press virtual buttons within the virtual environment, to push against surfaces, to grasp and hold objects, and so forth. 
     A computer  110 , often referred to as a gaming console, may be used in conjunction with the VR controllers  106  and  108  to perform calculations and to generate views of the virtual environment in response to user movements for display by the VR headset  106 . The VR controllers may communicate wirelessly with the computer  110  using Bluetooth, WiFi, or other wireless technologies. The VR controllers may also communicate with the computer  110  via the VR headset  106 , which may be connected to computer  110  via one or more wires or wirelessly. 
     The physical space  102  has multiple stationary emitters  112 , shown in  FIG. 1  as a first emitter  112 ( a ) and a second emitter  112 ( b ), that are mounted on the walls or ceiling of the space  102 , directed inwardly with respect to the room. Each emitter  112  emits optical reference signals that are received by the VR controllers  106  and  108  to determine angular position information. Specifically, the VR controllers have optical sensors (not shown in  FIG. 1 ) that receive and analyze the emitted optical reference signals to determine the position and pose of the user  104  relative to the emitters  112  and the space  102 . In the described embodiments, the optical signals are in the infrared range and are not visible by the user  104 . 
       FIG. 2  shows the VR headset  106  in more detail. The headset  106  has a front, outward surface  202  having multiple optical sensors  204  that are distributed and arranged so that they can receive infrared optical signals from different directions. The headset  106  has a headband  206 , along which additional sensors (not shown) may be positioned. In some embodiments, the VR headset  106  may comprise a helmet or cap, and sensors may be located at various additional positions on the top of the helmet or cap, to receive optical signals from additional directions. 
       FIG. 3  shows one of the VR hand controllers  108  in more detail. The VR hand controller  108  has various surfaces on which optical sensors  302  are positioned. The optical sensors  302  are arranged to receive optical signals from various different directions. The VR hand controller  108  may have buttons, sensors, lights, controls, knobs, indicators, displays, etc., allowing interaction by the user  104  in various ways. 
     The techniques described herein may be used for various types of position tracking devices, not limited to VR controllers. Some VR controllers may also have inertial measurement units (IMUs) that can be used for motion detection. 
     Referring again to  FIG. 1 , each emitter  112  may be configured to repeatedly sweep a laser line  114  through the space  102 . The laser line  114  may be generated by a line-projecting laser emitter in conjunction with a rotating mirror, as one example. In  FIG. 1 , the laser line  114  is projected as a horizontal line that sweeps vertically upward. An individual emitter  112  may also project a laser line as a vertical line that sweeps horizontally. In some embodiments, each emitter  112  may alternately project a vertically sweeping laser line and a horizontally sweeping laser line. 
     As the laser line  114  moves across or through the space  102 , at some point in time a portion of the laser line  114  will be projected onto the user  104  and will impinge on one or more of the sensors  204  and  302  of the VR controllers  106  and  108 . The laser line  114  will be detected by any of the sensors that are generally facing the emitter  112  and that are not blocked by the user  104  or by other objects. 
     For any given sweep or scan of the laser line  114 , it may happen that one or more of the sensors  204  or  302  do not receive or detect the laser line  114 . As will be explained in more detail below, these sensors may be disabled during one or more subsequent laser line sweeps in order to reduce power consumption. For example, when a given sensor does not detect the laser line during a first sweep of the laser line, that sensor may be disabled during a subsequent second sweep of the laser line, and then re-enabled for a third sweep of the laser line. The optical sensors consume significant power, and disabling any of the sensors can significantly improve battery life of the VR controllers. 
       FIG. 4  illustrates a technique for determining an angular coordinate of a VR controller or other position tracking device relative to a single stationary emitter, such as may be performed using the components discussed above. The upper part of  FIG. 4 , as well as of  FIGS. 5 and 6 , is a timeline showing optical signal transmissions by a stationary emitter during a single emitter cycle. The lower part of  FIG. 4 , as well as of  FIGS. 5 and 6 , is a timeline showing optical signal reception by an optical sensor of a VR controller during the emitter cycle. 
     During each of multiple emitter cycles, the emitter produces a short, omni-directional synchronization pulse  402  and a longer swept laser line  404 . In the illustrated example, the laser line  404  is swept through angles of 10° through 170° at a constant, known angular speed, starting at a fixed, known time after the synchronization pulse  402 . The projected angle of the laser line at any time is a linear function of the time elapsed since the most recent synchronization pulse. Note that in some embodiments, there may be more than one synchronization pulse  402 . 
     The optical sensor detects a first signal  406  corresponding to the omni-directional synchronization pulse  402  and a second signal  408  corresponding to the laser line as it passes over and impinges on the optical sensor for a relatively brief time. The angle of the laser line at the time when it impinges on the optical sensor is a linear function of the time t 0  between the first signal  406  and the second signal  408 . 
       FIG. 5  shows that a single emitter may be configured to generate two swept laser lines that sweep horizontally and vertically, respectively. In this case, a single emitter cycle may comprise a first synchronization pulse  502  and a corresponding sweep  504  of a laser line in a horizontal or X direction, and a second synchronization pulse  506  and a corresponding sweep  508  of a laser line in a vertical or Y direction. An optical sensor receives a horizontal synchronization signal  510  and a corresponding horizontal laser pulse  512  as the horizontally swept laser line passes over the sensor. The horizontal angle of the sensor relative to the emitter is calculated based on the time t x  between the horizontal synchronization signal  510  and the horizontal laser pulse  512 . The same sensor receives a vertical synchronization signal  514  and a corresponding vertical laser pulse  516  as the vertically swept laser line passes over the sensor. The vertical angle of the sensor relative to the emitter is calculated based on the time t y  between the vertical synchronization signal  514  and the vertical laser pulse  516 . 
     Emitter cycles of the first emitter  112 ( a ) and the second emitter  112 ( b ) may be interleaved, allowing the VR controller to determine angular coordinates relative to either or both of the first emitter  112 ( a ) and the second emitter  112 ( b ). A three-dimensional position and pose of the VR controller can be calculated based on these coordinates, derived from monitoring multiple sensors, assuming that the positions of the emitters  112 ( a ) and  112 ( b ) are known. 
       FIG. 6  illustrates another technique for specifying angular coordinates of a VR controller or other position tracking device relative to a single stationary emitter. In this example, laser transmissions of the emitter are continuously modulated and encoded/or to indicate the current angular coordinate of a swept laser line. Specifically, laser emissions are encoded to indicate, at any point in time, the instantaneous projected angle of the laser line relative to the emitter. This removes the need for a synchronization pulse, so that an emitter cycle comprises a horizontal or X sweep  602  of a laser line and a subsequent vertical or Y sweep  604  of a laser line. When the sensor detects the laser lines at  606  and  608 , the laser signals are demodulated or decoded to determine the current angular directions of the laser lines. 
       FIG. 7  illustrates an example method  700  of detecting optical reference signals for position detection. The method  700  may be performed by control logic of a position tracking device having multiple optical sensors mounted to receive infrared optical signals from multiple directions. The VR controllers described above are examples of position tracking devices. 
     The method  700  is performed for each of multiple emitter cycles. In the examples described herein, as illustrated by  FIGS. 4-6 , each emitter cycle comprises one or more swept laser lines generated by one or more emitters that are at a common location. In some embodiments, an emitter cycle may also comprise one or more synchronization pulses. 
     In the example of  FIG. 4 , each emitter cycle comprises an omni-directional synchronization pulse and a following laser line that sweeps through a space, producing the pulse  408  as the laser line passes over a sensor. 
     In the example of  FIG. 5 , each emitter cycle comprises a horizontal measurement cycle and a vertical measurement cycle. The horizontal measurement cycle comprises an omni-directional synchronization pulse and a following laser line that sweeps horizontally through a space to produce the pulse  512  as the laser line passes over a sensor. The vertical measurement cycle comprises an omni-directional synchronization pulse and a following laser line that sweeps vertically through the space to produce the pulse  516  as the laser line passes over a sensor. 
     In the example of  FIG. 6 , each emitter cycle comprises a first laser line that sweeps horizontally through a space to produce a laser pulse  606  and a following second laser line that sweeps vertically through the space to produce the laser pulse  608  as the laser line passes over a sensor. In the example of  FIG. 6 , each laser line is modulated or otherwise encoded to indicate a current, instantaneous projection angle of the laser line. 
       FIG. 7  illustrates actions that are performed with respect to signals emitted from a single stationary emitter, or from multiple emitters at a single location. Some embodiments may include multiple stationary emitters, at different locations, and the method  700  may be performed independently for the emitter cycles of each emitter or emitter location. 
     An action  702  comprises receiving an optical reference signal from a stationary emitter using at least one of multiple optical sensors that are mounted on the position tracking device. In the embodiments described herein, the action  702  comprises receiving and detecting a swept laser line using the sensors of the position tracking device. The laser line may be received and detected by multiple currently enabled sensors of the position tracking device, wherein individual sensors are enabled and disabled in accordance with subsequent actions of  FIG. 7 . In some cases, the swept laser line may be created using a laser signal that has been coded to specify a position coordinate that varies in accordance with the current projection angle of the laser line. 
     An action  704  comprises analyzing the optical reference signal to determine a position coordinate relative to the stationary emitter. As described above, the optical reference signal may comprise a swept laser line, and the action  704  may comprise (a) determining the time difference between detecting the swept laser line and a receiving a preceding synchronization signal, and (b) determining an angular position coordinate of the position tracking device based at least in part on the time difference. In other cases, the action  704  may comprise decoding angular position information from a received laser signal. 
     Note that the action  704  may be performed in part by a support component other than the VR controller, such as by the computer  110  of  FIG. 1 . For example, in some cases the VR controller may report a time difference to the computer  110 , and the computer  110  may use the time difference to compute the angular position coordinate. The computer  110  may further use calculated angular position coordinates from multiple emitters, at multiple locations, to determine a three-dimensional position and pose of the VR controller. 
     An action  706  comprises identifying any of the multiple optical sensors that did not receive or detect the optical reference signal during the emitter cycle. These optical sensors are referred to herein as non-receiving sensors. 
     An action  708  comprises enabling or disabling individual sensors to reduce power consumption, based at least in part on the action  706  of identifying non-receiving sensors. Generally, the action  708  comprises disabling any non-receiving sensor for a subsequent emitter cycle, and then re-enabling the non-receiving sensor after the subsequent emitter cycle. In some embodiments, the action  708  may comprise disabling each non-receiving sensor for a number of subsequent emitter cycles. In some cases, the number of subsequent emitter cycles during which the sensor is disabled may be dependent on whether the position tracking device is moving and/or the speed at which the position tracking device is moving. 
       FIGS. 8A, 8B, 8C, and 8D  illustrate several ways in which the action  708  may be implemented. The illustrated actions of each of these figures are performed with respect to each sensor of a VR controller or other position tracking device, and are repeated for each emitter cycle. 
     In  FIG. 8A , an action  802  comprises determining whether a sensor received and detected the optical reference signal of the current emitter cycle. If the sensor did receive and detect the optical reference signal, an action  804  is performed of enabling the sensor for a subsequent emitter cycle. 
     If the sensor did not receive and detect the optical reference signal, an action  806  is performed. The action  806  comprises determining whether the sensor was disabled during the current emitter cycle. If the sensor was disabled, the action  804  is performed of enabling the sensor for the subsequent emitter cycle. 
     If the sensor was not disabled during the current emitter cycle, an action  808  is performed of disabling the sensor for the subsequent emitter cycle. 
       FIG. 8B  shows an example implementation that is similar to that of  FIG. 8A , except for an additional action  810 . Before performing the action  806  of disabling a non-receiving sensor, the action  810  is performed to determine whether the non-receiving sensor is adjacent another sensor that did receive the optical reference signal during the emitter cycle. The action  808  is performed if the sensor is not adjacent to another sensor that did receive the optical reference signal. In response to determining that the sensor is adjacent to another sensor that did receive the optical reference signal, the action  804  is performed of enabling the sensor for the subsequent emitter cycle, even though the sensor may not have received the optical reference signal in the current emitter cycle. 
       FIG. 8C  shows an example implementation that is similar to that of  FIG. 8A , except for the addition of an action  812  that is performed initially, before other illustrated actions. The action  812  comprises determining whether the position tracking device is moving. If the position tracking device is moving, the action  804  is performed of enabling the sensor for the subsequent emitter cycle, regardless of whether the sensor is a receiving sensor or a non-receiving sensor. The other actions of  FIG. 8C  are performed if the position tracking device is not moving. 
     Whether the position tracking device is moving may be determined, as an example, by monitoring an accelerometer or inertial monitoring device (IMU) of the position tracking device. As another example, movement of the position tracking device may be determined by monitoring previous position calculations that were made using the previously determined angular coordinates. 
       FIG. 8D  shows an example implementation that is similar to that of  FIG. 8A . In this example, before performing the action  808  of disabling a non-receiving sensor, an action  814  is performed of determining a variable number of emitter cycles for which the non-receiving sensor will be disabled. The action  808  then comprises disabling the non-receiving sensor for the determined number of emitter cycles. The action  806  is modified to determine, during each iteration of the method  800 , whether a non-receiving sensor has been disabled for the determined number N of cycles. If the non-receiving sensor has been disabled for the determined number of cycles, the action  804  is performed of enabling the sensor. If the non-receiving sensor has not already been disabled for N emitter cycles, the action  814  is performed. For a sensor that has already been disabled, the action  814  may comprise incrementing or decrementing a counter, such as by incrementing decrementing N, in order to track the number of cycles during which the emitter has been disabled. 
     The action  814  may be based on various factors. For example, the variable number N may account for previously detected movement of the position tracking device, and N may be made smaller if the position tracking device is or has been moving. As another example, the action  814  may include detecting a speed at which the position tracking device is moving, and N may be based at least in part on the speed of the position tracking device. That is, N may be made larger when the position tracking device is moving more slowly, and smaller when the position tracking device is moving faster. N may also depend on external input, such as input regarding an expected position detection performance, such as sensitivity, accuracy, and/or latency. For example, a game or other application that is using information generated based on information provided by the VR controller may specify, during operation, varying levels of expected position detection performance. N may be made smaller to achieve higher performance, and larger when such performance is not needed in order to conserve battery usage. 
     The variations shown in  FIGS. 8A, 8B, 8C, and 8D , as well as other variations, may be used individually or may be combined and used together. 
       FIG. 9  illustrates an example method of enabling and disabling sensors that may be used in some embodiments. In some embodiments, each sensor may be either enabled or disabled during an entire emitter cycle. In other embodiments, as shown in  FIG. 9 , sensors may be disabled during a portion of an emitter cycle and enabled during another portion of the emitter cycle. The actions of  FIG. 9  are performed individually for each sensor. 
     An action  902  comprises predicting an expected arrival time of an optical reference signal based on an observed arrival time of the optical reference signal during a previous emitter cycle. In many cases, the optical signal can be reliably predicted to arrive at a time that is the same as or close to the same as its previous arrival time in the previous emitter cycle. Accordingly, the predicted arrival time for a given emitter cycle may be determined as being the actual arrival time of the optical reference signal in the previous emitter cycle. 
     An action  904  comprises determining whether the sensor has been otherwise disabled for the current emitter cycle, such as being disabled using any of the methods shown by  FIG. 8A, 8B, 8C , or  8 D. If the sensor has been disabled, an action  906  is performed of specifying a first time span within the current emitter cycle, where the first time span encompasses the predicted arrival time of the optical reference signal. An action  908  is then performed of disabling the sensor during portions of the emitter cycle other than the specified first time span. That is, the sensor is disabled at times during the emitter cycle other than the first time span, but enabled during the first time span. 
     If the sensor has not been otherwise disabled by actions  FIG. 8A, 8B, 8C , or  8 D, an action  910  is performed of specifying a second time span within the current emitter cycle, where the second time span is longer than the first time span. In certain embodiments, the second time span may encompass both the predicted arrival time and the first time span. The action  908  is then performed of disabling the sensor during portions of the emitter cycle other than the specified second time span. That is, the sensor is enabled during the second time span, but disabled at times during the emitter cycle other than the first time span. 
     The second time span may be specified as being longer than the first time span to account for potential movement of the position tracking device in the time between emitter cycles. In some cases, the second time span may comprise most or all of the emitter cycle. 
       FIG. 10  illustrates example components of a VR headset  1000  that may embody features and techniques described herein. A VR headset is illustrated as an example of various different types of VR controllers, wearable devices, and/or position tracking devices, which may be used in conjunction with the described features and techniques. 
     The VR headset  1000  may be implemented as a standalone device that is to be worn by a user. In some embodiments, the VR headset  1000  comprises a virtual reality (VR) or augmented reality (AR) headset that includes a near-eye or near-to-eye display(s). 
     In the illustrated implementation, the VR headset  1000  includes one or more processors  1002  and memory  1004  (e.g., computer-readable media). In some implementations, the processor(s)  1002  may include a central processing unit (CPU), a graphics processing unit (GPU), both CPU and GPU, a microprocessor, a digital signal processor or other processing units or components known in the art. Alternatively, or in addition, the functionally described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip systems (SOCs), complex programmable logic devices (CPLDs), etc. Additionally, each of the processor(s)  1002  may possess its own local memory, which also may store program modules, program data, and/or one or more operating systems. 
     The memory  1004  may include volatile and nonvolatile memory, removable and non-removable media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. Such memory includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, RAID storage systems, or any other medium which can be used to store the desired information and which can be accessed by a computing device. The memory  1004  may be implemented as computer-readable storage media (“CRSM”), which may be any available physical media accessible by the processor(s)  1002  to execute instructions stored on the memory  1004 . In one basic implementation, CRSM may include random access memory (“RAM”) and Flash memory. In other implementations, CRSM may include, but is not limited to, read-only memory (“ROM”), electrically erasable programmable read-only memory (“EEPROM”), or any other tangible medium which can be used to store the desired information and which can be accessed by the processor(s)  1002 . 
     Several modules such as instruction, datastores, and so forth may be stored within the memory  1004  and configured to execute on the processor(s)  1002 . A few example functional modules are shown as applications stored in the memory  1004  and executed on the processor(s)  1002 , although the same functionality may alternatively be implemented in hardware, firmware, or as a system on a chip (SOC). 
     An operating system module  1006  may be configured to manage hardware within and coupled to the VR headset  1000  for the benefit of other modules. In addition, in some instances the VR headset  1000  may include one or more applications  1008  stored in the memory  1004  or otherwise accessible to the VR headset  1000 . In this implementation, the application(s)  1008  include a gaming application  1010 . However, the VR headset  1000  may include any number or type of applications and is not limited to the specific example shown here. The gaming application  1010  may be configured to initiate gameplay of a video-based, interactive game (e.g., a VR game) that is playable by a user. 
     Generally, the VR headset  1000  has input devices  1012  and output devices  1014 . The input devices  1012  may include control buttons. In some implementations, one or more microphones may function as input devices  1012  to receive audio input, such as user voice input. In some implementations, one or more cameras or other types of sensors (e.g., inertial measurement unit (IMU)) may function as input devices  1012  to receive gestural input, such as a hand and/or head motion of the user. In some embodiments, additional input devices  1012  may be provided in the form of a keyboard, keypad, mouse, touch screen, joystick, and the like. In other embodiments, the VR headset  1000  may omit a keyboard, keypad, or other similar forms of mechanical input. Instead, the VR headset  1000  may be implemented using relatively simplistic forms of the input device  1012 , a network interface (wireless or wire-based), power, and processing/memory capabilities. For example, a limited set of one or more input components may be employed (e.g., a dedicated button to initiate a configuration, power on/off, etc.) so that the VR headset  1000  can thereafter be used. In one implementation, the input device(s)  1012  may include control mechanisms, such as basic volume control button(s) for increasing/decreasing volume, as well as power and reset buttons. 
     The output devices  1014  may include a display  1016 , a light element (e.g., LED), a vibrator to create haptic sensations, a speaker(s) (e.g., headphones), and/or the like. There may also be a simple light element (e.g., LED) to indicate a state such as, for example, when power is on. The electronic display(s)  1016  shown in  FIG. 10  may function as output devices  1014  to output visual/graphical output. 
     The VR headset  1000  may further include a wireless unit  1018  coupled to an antenna  1020  to facilitate a wireless connection to a network. The wireless unit  1018  may implement one or more of various wireless technologies, such as Wi-Fi, Bluetooth, etc. It is to be appreciated that the VR headset  1000  may further include physical ports to facilitate a wired connection to a network, a connected peripheral device, or a plug-in network device that communicates with other wireless networks. 
     The VR headset  1000  may further include an optical subsystem  1022  that directs light from the electronic display  1016  to a user&#39;s eye(s) using one or more optical elements. The optical subsystem  1022  may include various types and combinations of different optical elements, including, without limitations, such as apertures, lenses (e.g., Fresnel lenses, convex lenses, concave lenses, etc.), filters, and so forth. In some embodiments, one or more optical elements in the optical subsystem  1022  may have one or more coatings, such as anti-reflective coatings. Magnification of the image light by the optical subsystem  1022  allows the electronic display  1016  to be physically smaller, weigh less, and consume less power than larger displays. Additionally, magnification of the image light may increase a field-of-view (FOV) of the displayed content (e.g., images). For example, the FOV of the displayed content is such that the displayed content is presented using almost all (e.g., 120-150 degrees diagonal), and in some cases all, of the user&#39;s FOV. AR applications may have a narrower FOV (e.g., about 40 degrees FOV). The optical subsystem  1022  may be designed to correct one or more optical errors, such as, without limitation, barrel distortion, pincushion distortion, longitudinal chromatic aberration, transverse chromatic aberration, spherical aberration, chromatic aberration, field curvature, astigmatism, and so forth. In some embodiments, content provided to the electronic display  1016  for display is pre-distorted, and the optical subsystem  1022  corrects the distortion when it receives image light from the electronic display  1016  generated based on the content. 
     The VR headset  1000  may further include one or more sensors  1024 , such as sensors used to generate motion, position, and orientation data. These sensors  1024  may be or include gyroscopes, accelerometers, magnetometers, video cameras, color sensors, or other motion, position, and orientation sensors. The sensors  1024  may also include sub-portions of sensors, such as a series of active or passive markers that may be viewed externally by a camera or color sensor in order to generate motion, position, and orientation data. 
     In one example, the sensor(s)  1024  may include an inertial measurement unit (IMU)  1026 . IMU  1026  may be an electronic device that generates motion data based on measurement signals received from accelerometers, gyroscopes, magnetometers, and/or other sensors suitable for detecting motion, correcting error associated with IMU  1026 , or some combination thereof. Based on the measurement signals such motion-based sensors, such as the IMU  1026 , may generate calibration data indicating an estimated position of VR headset  1000  relative to an initial position of VR headset  1000 . For example, multiple accelerometers may measure translational motion (forward/back, up/down, left/right) and multiple gyroscopes may measure rotational motion (e.g., pitch, yaw, and roll). The IMU  1026  can, for example, rapidly sample the measurement signals and calculate the estimated position of VR headset  1000  from the sampled data. For example, IMU  1026  may integrate measurement signals received from the accelerometers over time to estimate a velocity vector and integrates the velocity vector over time to determine an estimated position of a reference point on VR headset  1000 . 
     As another example, the sensors  1024  may include optical light sensors  1028 , which may be used as described above for detecting optical signals and for determining the position and pose of the VR headset  1000 . The light sensors  1028  may comprise infrared light-sensitive photo diodes, as an example. 
     The VR headset  1000  may further include an eye tracking module  1030 . A camera or other optical sensor inside VR headset  1000  may capture image information of a user&#39;s eyes, and the eye tracking module  1030  may use the captured information to determine interpupillary distance, interocular distance, a three-dimensional (3D) position of each eye relative to VR headset  1000  (e.g., for distortion adjustment purposes), including a magnitude of torsion and rotation (i.e., roll, pitch, and yaw) and gaze directions for each eye. In one example, infrared light is emitted within VR headset  1000  and reflected from each eye. The reflected light is received or detected by a camera of the VR headset  1000  and analyzed to extract eye rotation from changes in the infrared light reflected by each eye. 
     Many methods for tracking the eyes of a user can be used by the eye tracking module  1030 . Accordingly, the eye tracking module  1030  may track up to six degrees of freedom of each eye (i.e., 3D position, roll, pitch, and yaw) and at least a subset of the tracked quantities may be combined from two eyes of a user to estimate a gaze point (i.e., a 3D location or position in the virtual scene where the user is looking). For example, the eye tracking module  1030  may integrate information from past measurements, measurements identifying a position of a user&#39;s head, and 3D information describing a scene presented by the electronic display  1016 . Thus, information for the position and orientation of the user&#39;s eyes is used to determine the gaze point in a virtual scene presented by the VR headset  1000  where the user is looking. 
     The VR headset  1000  may further include a head tracking module  1032 . The head tracking module  1032  may leverage one or more of the sensors  1024  to track head motion of the user, as described above. 
     Although the subject matter has been described in language specific to structural features, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features described. Rather, the specific features are disclosed as illustrative forms of implementing the claims.