Patent Publication Number: US-2015084864-A1

Title: Input Method

Description:
BACKGROUND 
     Wearable computers include electronic devices that may be worn by a user. As examples, wearable computers can be under or on top of clothing or integrated into eye glasses. There may be constant interaction between a wearable computer and a user. The wearable computer may be integrated into user activities and may be considered an extension of the mind and/or body of the user. 
     The wearable computer may include an image display element close enough to an eye of a wearer such that a displayed image fills or nearly fills a field of view associated with the eye, and appears as a normal sized image, such as might be displayed on a traditional image display device. The relevant technology may be referred to as “near-eye displays.” Near-eye displays may be integrated into wearable displays, also sometimes called “head-mounted displays” (HMDs). 
     SUMMARY 
     The present application discloses systems and methods to unlock a screen using eye tracking information. In one aspect, a method is described. The method may comprise generating a display of a random content on a head-mounted display (HMD) of a wearable computing system. The random content may at least include among other content a content personalized to a user of the wearable computing system including one or more of a name and a picture associated with the user. The wearable computing system may be operable to be in a locked mode of operation and may include an eye tracking system. The method may also comprise receiving information associated with a gaze location of an eye of the user from the eye tracking system. The method may further comprise determining that the gaze location substantially matches a predetermined location of the content personalized to the user on the HMD. The method may also comprise determining that a responsiveness metric is less than a predetermined threshold. The responsiveness metric may include a time period elapsed between generating the display of the random content on the HMD and determining that the gaze location substantially matches the predetermined location of the content personalized to the user on the HMD. The method may further comprise authenticating the user. Authenticating the user may comprise a switch from the wearable computing system being in the locked mode of operation to being in an unlocked mode of operation. Functionality of the wearable computing system may be reduced in the locked mode as compared to the unlocked mode. 
     In another aspect, a computer readable memory having stored therein instructions executable by a computing device to cause the computing device to perform functions is described. The functions may comprise generating a display of a random content on a head-mounted display (HMD) of a wearable computing system. The random content may at least include among other content a content personalized to a user of the wearable computing system including one or more of a name and a picture associated with the user. The wearable computing system may be operable to be in a locked mode of operation and may include an eye tracking system. The functions may also comprise receiving information associated with a gaze location of an eye of the user from the eye tracking system. The functions may further comprise determining that the gaze location substantially matches a given location of the content personalized to the user on the HMD. The functions may also comprise determining that a responsiveness metric is less than a predetermined threshold. The responsiveness metric may include a time period elapsed between generating the display of the random content on the HMD and determining that the gaze location substantially matches the given location of the content personalized to the user on the HMD. The functions may further comprise authenticating the user. Authenticating the user may comprise a switch from the wearable computing system being in the locked mode of operation to being in an unlocked mode of operation. Functionality of the wearable computing system may be reduced in the locked mode as compared to the unlocked mode. 
     In still another aspect, a system is described. The system may comprise a wearable computer including a head-mounted display (HMD). The wearable computer may be operable to be in a locked mode of operation. The system may also comprise an eye tracking system in communication with the wearable computer. The eye tracking system may be configured to track eye movement of a user of the wearable computer. The system may further comprise a processor in communication with the wearable computer and the eye tracking system. The processor may be configured to generate a display of a plurality of moving objects on a display of the HMD. The processor may also be configured to receive information associated with the eye movement from the eye tracking system. Based on the information associated with the eye movement, the processor may further be configured to determine that a path associated with the eye movement substantially matches a path of a given moving object of the plurality of moving objects. A characteristic associated with the given moving object may match a predetermined characteristic. The processor may further be configured to authenticate the user. Authenticating the user may comprise a switch from the wearable computing system being in the locked mode of operation to being in an unlocked mode of operation. Functionality of the wearable computing system may be reduced in the locked mode as compared to in the unlocked mode. 
     The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the figures and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a block diagram of an example wearable computing and head-mounted display system, in accordance with an example embodiment. 
         FIG. 2A  illustrates a front view of a head-mounted display (HMD) in an example eyeglasses embodiment. 
         FIG. 2B  illustrates a side view of the HMD in the example eyeglasses embodiment. 
         FIG. 3  is a flow chart of an example method to authenticate a user using eye tracking information. 
         FIG. 4  is a diagram illustrating the example method to authenticate the user using eye tracking information depicted in  FIG. 3 . 
         FIG. 5  is a flow chart of another example method to authenticate a user using eye tracking information. 
         FIG. 6  is a diagram illustrating the example method to authenticate a user using eye tracking information depicted in  FIG. 5 . 
         FIG. 7  is a functional block diagram illustrating an example computing device used in a computing system that is arranged in accordance with at least some embodiments described herein. 
         FIG. 8  is a schematic illustrating a conceptual partial view of an example computer program product that includes a computer program for executing a computer process on a computing device, arranged according to at least some embodiments presented herein. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description describes various features and functions of the disclosed systems and methods with reference to the accompanying figures. In the figures, similar symbols identify similar components, unless context dictates otherwise. The illustrative system and method embodiments described herein are not meant to be limiting. It may be readily understood that certain aspects of the disclosed systems and methods can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein. 
     This disclosure may disclose, inter alia, systems and methods for authenticating a user using eye tracking information. A wearable computing system may include a head mounted display (HMD). The wearable computing system may be operable to be in a locked mode of operation after a period of inactivity by a user. Locked mode of operation may include a locked screen and reduced functionality of the wearable computing system. The user may be authenticated to be able to use the wearable computing system after the period of inactivity. To authenticate the user, the wearable computing system may generate a display of a random content on the HMD. The random content may include a content personalized to the user. The wearable computing system may receive information associated with a gaze location of an eye of the user and determine that the gaze location substantially matches a predetermined location of the content personalized to the user on the HMD and authenticate the user. 
     The content personalized to the user may include names and pictures associated with the user such as names and pictures of the user or people or objects related to the user (e.g., wife, children, etc.). The user may be able to identify the content personalized to the user faster than another person who may not be as familiar as the user with the content personalized to the user. The wearable computing system may determine a responsiveness metric that includes a time period elapsed between generating the display of the random content and determining that the gaze location of the eye of the user substantially matches the predetermined location on the HMD of the content personalized to the user. The responsiveness metric may be determined to be less than a predetermined threshold indicating that the user identified the content personalized to the user within a predetermined time period. Identifying the content personalized to the user within the predetermined time period that may indicate familiarity with the content personalized to the user and the user may be authenticated. 
     In another example, to authenticate the user after a period of inactivity that may have caused the screen to be locked, a processor coupled to the wearable computing system may generate a display of a plurality of moving objects. Each of the plurality of moving objects may have a unique characteristic, such as shape or color. Paths of the plurality of moving objects may be randomly generated. The processor may detect through an eye tracking system coupled to the wearable computing system if an eye of a wearer of the HMD may be tracking a moving object with a predetermined characteristic. The processor may determine that a path associated with the movement of the eye of the wearer matches or substantially matches a path of the moving object and may authenticate the user. Tracking a slowly moving object may reduce a probability of eye blinks, or rapid eye pupil movements (i.e., saccades) disrupting the eye tracking system. The processor may generate the display of the plurality of moving objects such that speeds associated with motion of the moving objects on the HMD may be less than a predetermined threshold speed. Onset of rapid eye pupil movements may occur if a speed of a moving object tracked by the eye of the wearer is equal to or greater than the predetermined threshold speed. Alternatively, the speed associated with the moving object may be independent of correlation to eye blinks or rapid eye movements. 
     The speed associated with the motion of the moving object may change, i.e., the moving object may accelerate or decelerate. The processor may track the eye movement of the eye of the wearer to detect if the eye movement may indicate that the eye movement may be correlated with changes in the speed associated with the motion of the moving object and may authenticate the user accordingly. 
     Alternative to the processor generating the display of the plurality of moving objects on the HMD, the processor may cause an image or a sequence of images including the random content or the plurality of moving objects to be projected on a retina of the eye of the wearer and may determine if the eye pupil of the wearer may be tracking the moving object with the predetermined characteristic in the sequence of images, for example. 
     The eye tracking system may comprise a camera that may continuously be enabled to monitor eye movement. The wearable computing system may alternatively include a sensor, which may consume less electric power than the camera, to detect if a user may attempt to use the wearable computing system after a period of inactivity and then enable the camera to cause the eye tracking system to be operable. The user may additionally perform a gesture to indicate an attempt to use the wearable computing system. For example, a gyroscope coupled to the HMD may detect a head tilt, for example, which may indicate that the wearer may be attempting to use the HMD and the wearable computing system may authenticate the user. 
     Referring now to the figures,  FIG. 1  is a block diagram of an example wearable computing and head-mounted display (HMD) system  100  that may include several different components and subsystems. Components coupled to or included in the system  100  may include an eye-tracking system  102 , a HMD-tracking system  104 , an optical system  106 , peripherals  108 , a power supply  110 , a processor  112 , a memory  114 , and a user interface  115 . Components of the system  100  may be configured to work in an interconnected fashion with each other and/or with other components coupled to respective systems. For example, the power supply  110  may provide power to all the components of the system  100 . The processor  112  may receive information from and may control the eye tracking system  102 , the HMD-tracking system  104 , the optical system  106 , and peripherals  108 . The processor  112  may be configured to execute program instructions stored in the memory  114  to generate a display of images on the user interface  115 . 
     The eye-tracking system  102  may include hardware such as an infrared camera  116  and at least one infrared light source  118 . The infrared camera  116  may be utilized by the eye-tracking system  102  to capture images of an eye of the wearer. The images may include either video images or still images or both. The images obtained by the infrared camera  116  regarding the eye of the wearer may help determine where the wearer may be looking within a field of view of the HMD included in the system  100 , for instance, by ascertaining a location of the eye pupil of the wearer. The infrared camera  116  may include a visible light camera with sensing capabilities in the infrared wavelengths. 
     The infrared light source  118  may include one or more infrared light-emitting diodes or infrared laser diodes that may illuminate a viewing location, i.e. an eye of the wearer. Thus, one or both eyes of a wearer of the system  100  may be illuminated by the infrared light source  118 . The infrared light source  118  may be positioned along an optical axis common to the infrared camera, and/or the infrared light source  118  may be positioned elsewhere. The infrared light source  118  may illuminate the viewing location continuously or may be turned on at discrete times. 
     The HMD-tracking system  104  may include a gyroscope  120 , a global positioning system (GPS)  122 , and an accelerometer  124 . The HMD-tracking system  104  may be configured to provide information associated with a position and an orientation of the HMD to the processor  112 . The gyroscope  120  may include a microelectromechanical system (MEMS) gyroscope or a fiber optic gyroscope as examples. The gyroscope  120  may be configured to provide orientation information to the processor  112 . The GPS unit  122  may include a receiver that obtains clock and other signals from GPS satellites and may be configured to provide real-time location information to the processor  112 . The HMD-tracking system  104  may further include an accelerometer  124  configured to provide motion input data to the processor  112 . 
     The optical system  106  may include components configured to provide images to a viewing location, i.e. an eye of the wearer. The components may include a display panel  126 , a display light source  128 , and optics  130 . These components may be optically and/or electrically-coupled to one another and may be configured to provide viewable images at the eye of the wearer. One or two optical systems  106  may be provided in the system  100 . In other words, the HMD wearer may view images in one or both eyes, as provided by one or more optical systems  106 . Also, the optical system(s)  106  may include an opaque display and/or a see-through display coupled to the display panel  126 , which may allow a view of the real-world environment while providing superimposed virtual images. The infrared camera  116  coupled to the eye tracking system  102  may be integrated into the optical system  106 . 
     Additionally, the system  100  may include or be coupled to peripherals  108 , such as a wireless communication interface  134 , a touchpad  136 , a microphone  138 , a camera  140 , and a speaker  142 . Wireless communication interface  134  may use 3G cellular communication, such as CDMA, EVDO, GSM/GPRS, or 4G cellular communication, such as WiMAX or LTE. Alternatively, wireless communication interface  134  may communicate with a wireless local area network (WLAN), for example, using WiFi. In some examples, wireless communication interface  134  may communicate directly with a device, for example, using an infrared link, Bluetooth, near field communication, or ZigBee. 
     The power supply  110  may provide power to various components in the system  100  and may include, for example, a rechargeable lithium-ion battery. Various other power supply materials and types known in the art are possible. 
     The processor  112  may execute instructions stored in a non-transitory computer readable medium, such as the memory  114 , to control functions of the system  100 . Thus, the processor  112  in combination with instructions stored in the memory  114  may function as a controller of system  100 . For example, the processor  112  may control the wireless communication interface  134  and various other components of the system  100 . In other examples, the processor  112  may include a plurality of computing devices that may serve to control individual components or subsystems of the system  100 . Analysis of the images obtained by the infrared camera  116  may be performed by the processor  112  in conjunction with the memory  114 . 
     In addition to instructions that may be executed by the processor  112 , the memory  114  may store data that may include a set of calibrated wearer eye pupil positions and a collection of past eye pupil positions. Thus, the memory  114  may function as a database of information related to gaze direction and location. Calibrated wearer eye pupil positions may include, for instance, information regarding extents or range of an eye pupil movement (right/left and upwards/downwards), and relative position of eyes of the wearer with respect to the HMD. For example, a relative position of a center and corners of an HMD screen with respect to a gaze direction or a gaze angle of the eye pupil of the wearer may be stored. Also, locations or coordinates of starting and ending points, or waypoints, of a path of a moving object displayed on the HMD, or of a static path (e.g., semicircle, Z-shape etc.) may be stored on the memory  114 . 
     The system  100  may further include the user interface  115  for providing information to the wearer or receiving input from the wearer. The user interface  115  may be associated with, for example, displayed images, a touchpad, a keypad, buttons, a microphone, and/or other peripheral input devices. The processor  112  may control functions of the system  100  based on input received through the user interface  115 . For example, the processor  112  may utilize user input from the user interface  115  to control how the system  100  may display images within a field of view or may determine what images the system  100  may display. 
     Although  FIG. 1  shows various components of the system  100  (i.e., wireless communication interface  134 , processor  112 , memory  114 , infrared camera  116 , display panel  126 , GPS  122 , and user interface  115 ) as being integrated into the system  100 , one or more of the described functions or components of the system  100  may be divided up into additional functional or physical components, or combined into fewer functional or physical components. For example, the infrared camera  116  may be mounted on the wearer separate from the system  100 . Thus, the system  100  may be part of a wearable computing device in the form of separate devices that can be worn on or carried by the wearer. Separate components that make up the wearable computing device may be communicatively coupled together in either a wired or wireless fashion. In some further examples, additional functional and/or physical components may be added to the examples illustrated by  FIG. 1 . In other examples, the system  100  may be included within other systems. 
     The system  100  may be configured as, for example, eyeglasses, goggles, a helmet, a hat, a visor, a headband, or in some other form that can be supported on or from a head of the wearer. The system  100  may be further configured to display images to both eyes of the wearer. Alternatively, the system  100  may display images to only one eye, either a left eye or a right eye. 
       FIG. 2A  illustrates a front view of a head-mounted display (HMD)  200  in an example eyeglasses embodiment.  FIG. 2B  presents a side view of the HMD  200  in  FIG. 2A .  FIGS. 2A and 2B  will be described together. Although this example embodiment is provided in an eyeglasses format, it will be understood that wearable systems and HMDs may take other forms, such as hats, goggles, masks, headbands and helmets. The HMD  200  may include lens frames  202  and  204 , a center frame support  206 , lens elements  208  and  210 , and an extending side-arm  212  that may be affixed to the lens frame  202 . There may be another extending side arm affixed to the lens frame  204  but is not shown. The center frame support  206  and side-arm  212  may be configured to secure the HMD  200  to a head of a wearer via a nose and an ear of the wearer. Each of the frame elements  202 ,  204 , and  206  and the extending side-arm  212  may be formed of a solid structure of plastic or metal, or may be formed of a hollow structure of similar material so as to allow wiring and component interconnects to be internally routed through the HMD  200 . Lens elements  208  and  210  may be at least partially transparent so as to allow the wearer to look through lens elements. In particular, a right eye  214  of the wearer may look through right lens  210 . Optical systems  216  and  218  may be positioned in front of lenses  208  and  210 , respectively. The optical systems  216  and  218  may be attached to the HMD  200  using support mounts such as  220  shown for the right optical system  216 . Furthermore, the optical systems  216  and  218  may be integrated partially or completely into lens elements  208  and  210 , respectively. 
     Although  FIG. 2A  illustrates an optical system for each eye, the HMD  200  may include an optical system for only one eye (e.g., right eye  214 ). The wearer of the HMD  200  may simultaneously observe from optical systems  216  and  218  a real-world image with an overlaid displayed image. The HMD  200  may include various elements such as a processor  222 , a touchpad  224 , a microphone  226 , and a button  228 . The processor  222  may use data from, among other sources, various sensors and cameras to determine a displayed image that may be displayed to the wearer. The HMD  200  may also include eye tracking systems  230  and  232  that may be integrated into the optical systems  216  and  218 , respectively. The locations of eye tracking systems  230  and  232  are for illustration only. The eye tracking systems  230  and  232  may be positioned in different locations and may be separate or attached to the HMD  200 . A gaze axis or direction  234  associated with the eye  214  may be shifted or rotated with respect to the optical system  216  or eye tracking system  230  depending on placement of the HMD  200  on the nose and ears of the wearer. The eye-tracking systems  230  and  232  may include hardware such as an infrared camera and at least one infrared light source, but may include other components also. In one example, an infrared light source or sources integrated into the eye tracking system  230  may illuminate the eye  214  of the wearer, and a reflected infrared light may be collected with an infrared camera to track eye or eye-pupil movement. Those skilled in the art would understand that other user input devices, user output devices, wireless communication devices, sensors, and cameras may be reasonably included in such a wearable computing system. 
     The HMD  200  may enable the wearer to observe surroundings of the wearer and also view a displayed image on a display of the optical systems  216  and  218 . In some cases, the displayed image may overlay a portion of a field of view of the wearer. Thus, while the wearer of the HMD  200  may be performing daily activities, such as walking, driving, exercising, etc., the wearer may be able to see a displayed image generated by the HMD  200  at the same time that the wearer may be looking out at the surroundings. The wearer may take off the HMD  200  or may stop using the HMD  200  for a period of time. After a period of inactivity by the wearer, the HMD  200  may lock a display screen coupled to the HMD  200  and reduce functionality of the HMD  200  to save power. The wearer may attempt to use the HMD  200  but may be authenticated by the HMD  200  before the wearer may be able to use the HMD  200  again. 
       FIG. 3  is a flow chart illustrating an example method  300  to authenticate a user using eye tracking information.  FIG. 4  is a diagram illustrating the example method  300  to authenticate a user using eye tracking information as depicted in  FIG. 3 , in accordance with at least some embodiments of the present disclosure.  FIGS. 3 and 4  will be described together. 
       FIGS. 3 and 4  illustrate the method  300  in a context of a wearable computing system including a head-mounted display integrated into eyeglasses. However, the method applies to any computing system for authenticating a user and unlocking a screen coupled to the computing system using eye tracking information. 
     Method  300  may include one or more operations, functions, or actions as illustrated by one or more of blocks  302 ,  304 ,  306 ,  308 , and  310 . Although the blocks are illustrated in a sequential order, these blocks may in some instances be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation 
     In addition, for the method  300  and other processes and methods disclosed herein, the flowchart shows functionality and operation of one possible implementation of present embodiments. In this regard, each block may represent a module, a segment, or a portion of program code, which includes one or more instructions executable by a processor for implementing specific logical functions or steps in the process. The program code may be stored on any type of computer readable medium, for example, such as a storage device including a disk or hard drive. The computer readable medium may include a non-transitory computer readable medium or memory, for example, such as computer-readable media that stores data for short periods of time like register memory, processor cache and Random Access Memory (RAM). The computer readable medium may also include non-transitory media or memory, such as secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media may also be any other volatile or non-volatile storage systems. The computer readable medium may be considered a computer readable storage medium, a tangible storage device, or other article of manufacture, for example. 
     In addition, for the method  300  and other processes and methods disclosed herein, each block in  FIG. 3  may represent circuitry that is wired to perform the specific logical functions in the process. 
     A wearable computing system including a head-mounted display (HMD) may operate in a locked mode of operation after a period of inactivity by a wearer or a user. The locked mode of operation may include locking a display screen coupled to the HMD and a reduction in a functionality of the wearable computing system to save power. For the user to be able to use the HMD again, the wearable computing system may authenticate the user. 
     At block  302 , method  300  includes generate a display of a random content including a content personalized to a user. To authenticate the user, a processor coupled to the wearable computing system may generate the display of the random content on the HMD. The random content may include the content personalized to the user. For example, the processor may generate a display of a grid including multiple random pictures. The grid may include multiple cells and a picture may be displayed in each cell, for example. One of the pictures in the grid may be associated with the user such as a picture of the user as a child, a picture of a wife, child, relative, or a friend of the user, a picture of a school where the user may have studied, a picture of an intersection close to where the user may have lived, or a picture of logos from institutions associated with the user (university logos, corporate logos, etc.). The processor may, for example, obtain the pictures associated with the user from a social networking account of the user. More than one picture in the grid may be associated with the user. In another example, the processor may display a grid of random names. A grid may include multiple cells and a name may be displayed in each cell, for example. One of the names in the grid may be associated with the user (e.g., a name of the user, a name of the wife, child, friend, or relative of the user). More than one picture in the grid may be associated with the user. The grid of random names or random pictures may include different pictures or names every time the wearable computing system may authenticate the user. 
     In other examples, the processor coupled to the wearable computing system may receive the generated display of random content from a server, and may provide the display on a screen of the HMD. 
       FIG. 4  illustrates the HMD integrated into eyeglasses.  FIG. 4  shows the right side of the eyeglasses for illustration. However, the method  300  may apply to both left and right sides. The HMD integrated into the eyeglasses in  FIG. 4  may, for example, be the HMD described in  FIG. 2 . 
     In  FIG. 4 , on a display screen or panel of the optical system  216 , the processor of the wearable computing system may generate a display of a grid  402  of random names, for example.  FIG. 4  shows the grid  402  including nine cells, each cell displaying a name. Other grid configurations may be possible. More or fewer cells may be displayed. A mix of names and pictures or any content may also be used. The grid  402  of random names may include names that may be unknown to the user and one or more names that may be known or personalized to the user (e.g., name of a wife, children, relative, friend, or acquaintance or of the user). 
     At block  304 , method  300  includes receive information associated with a gaze location of an eye of the user. For example, in  FIG. 4 , the eye tracking system  230  may track eye movement of the eye  214  of the user. The eye tracking system  230  may, for example, track movements of an eye pupil  404  and a gaze axis  406  associated with the eye  214  and eye pupil  404 . As the eye  214  or eye pupil  404  moves, the eye tracking system  230  may track a gaze location  408  on the HMD associated with the gaze axis  406 . The processor coupled to the wearable computing system may receive the information associated with the gaze location  408  from the eye tracking system  230 . 
     In one example, the eye tracking system  230  may be continuously enabled to monitor the eye  214  of the user. In another example, the eye tracking system  230  may be disabled until another sensor or input to the wearable computing system may indicate an attempt by the user to activate the HMD after a period of inactivity, for example. The wearable computing system may accordingly attempt to authenticate the user. For example, the user may perform a gesture such as head tilt or head shake. A gyroscope coupled to the wearable computing system may detect such gesture. The processor coupled to the wearable computing system may receive information associated with the gyroscope indicating the gesture and may interpret the gesture as an attempt by the user to activate and use the HMD. As another example, the user may press a button coupled to the wearable computing system to indicate an attempt to activate the HMD. Upon detecting the attempt, the processor may enable the eye tracking system  230 . As yet another example, a low power reflectivity sensor system that detects if the eye pupil  404  may be pointing or gazing at the screen may be used to detect the attempt. The low power reflectivity sensor system may include an infrared (IR) light emitting diode (LED) and photo detector that may be directed at the eye pupil  404 . When the eye pupil  404  may be gazing at the IR LED to attempt to unlock the screen, the amount of IR light reflected back to the photo detector may drop, for example. Using another sensor, gesture, a button, or the amount of IR light reflected back to the photo detector to indicate the attempt and consequently enabling the eye tracking system  230  may save power since the eye tracking system  230  may not be running continuously. 
     At decision block  306 , method  300  determines whether the gaze location associated with the eye  214  of the user substantially matches a predetermined location of the content personalized to the user. Based on the information associated with the gaze location  408  of the eye  214 , the processor may compare the gaze location  408  with the predetermined location of the content personalized to the user. For example, in  FIG. 4 , the gaze location  408  matches a location of a cell of the grid  402  displaying “Name 8”. If “Name 8” is associated with the user and includes the content personalized to the user, then the processor may determine that the gaze location  408  substantially matches the predetermined location of the content personalized to the user, “Name 8” in this case.  FIG. 4  shows rectangular cells containing the random content and the content personalized to the user. The processor may determine that if the gaze location is in a rectangular area containing “Name 8”, i.e., the content personalized to the user, then the gaze location may substantially match the predetermined location of the content personalized to the user, for example. In another example, the processor may determine a circular area with a given radius contained in the cell containing the content personalized to the user. If the gaze location is in the circular area, then the gaze location may substantially match the predetermined location of the content personalize to the user. Other geometric shapes and areas may be used to determine an area such that if the gaze location is in the area, then the gaze location may substantially match the predetermined location of the content personalized to the user. 
     In some examples, the processor may adjust the gaze location associated with the eye  214  of the user before comparing the gaze location to the predetermined location of the content personalized to the user. For example, placement of eyeglasses including the wearable computing system and the HMD on ears and a nose of the user may be slightly different every time the user wears the eyeglasses after taking the eyeglasses off. A relative location of the eye with respect to a camera coupled to the eye tracking system  230  or a relative location of the gaze axis  406  associated with the eye  214  with respect to a reference axis associated with the HMD may vary. Therefore, the processor may apply a transform to the gaze location  408  to compensate for a difference in the relative location. The transform may, for example, include an offset of the gaze location  408  to compensate for a shift in the gaze axis  406  of the eye  214  of the user of the HMD with respect to the reference axis associated with the HMD. The transform may comprise a rotational adjustment to compensate for a rotation in the gaze axis  406  of the eye  214  of the user of the HMD with respect to the reference axis associated with the HMD. The transform may further comprise a scale factor that may compensate for a distance between a camera, coupled to the eye tracking system, monitoring the eye movement of the wearer, or a reference point on the HMD, and the eye of the wearer. As a position of the camera or the reference point changes (e.g., farther or closer to the eye of the wearer) the scale factor may compensate for the change in position of the camera or the reference point with respect to the eye of the wearer. 
     If the gaze location  408  does not substantially match the predetermined location of the content personalized to the user, the HMD may remain in a locked and an authentication of the user may fail. 
     At block  308 , if the gaze location  408  matches or substantially matches the predetermined location of the content personalized to the user, possibly after an adjustment of the gaze location by the processor, the method  300  may determine whether a responsiveness metric is less than a predetermined threshold or not. The user may be able to identify and gaze at the content personalized to the user faster than another person who may not be familiar with the content personalized to the user. The user may, for example, recognize the name of the user in a grid of random names in a period of time less than a predetermined period of time or threshold and quicker than any other person. A responsiveness of the user may be quantified by a responsiveness metric. The responsiveness metric may include a time period elapsed between generating the display of the random content and determining that the gaze location  408  substantially matches the predetermined location of the content personalized to the user on the HMD. A person who may not be familiar with the content personalized to the user may not be able to identify and gaze at the content personalized to the user or may take a longer period of time to identify and gaze at the content personalized to the user than the user. 
     If the responsiveness metric is greater than the predetermined period of time or threshold, the HMD may remain in a locked and an authentication of the user may fail. 
     At block  310 , if the responsiveness metric is less than the predetermined period of time or threshold, method  300  includes authenticate the user. The wearable computing system may switch to be in an unlocked mode of operation and may allow the user to use the HMD and the method  300  terminates. 
     In another example, the method  300  may include additional or alternative functions. For example, the processor may generate the content personalized to the user to be displayed in more than one location on the HMD. For example, the random content may be a grid of nine pictures; three of the nine pictures may be associated with the user. The user may gaze at the three pictures associated with the user in a given sequence. The processor may receive information associated with a sequence of gaze locations of the eye of the user. The processor may also receive information associated with temporal characteristics of eye movement of the user between gaze locations of the sequence of gaze locations. The temporal characteristics may include time periods elapsed between the gaze locations. The processor may determine that the sequence of gaze locations and temporal characteristics of the eye movement between the gaze locations substantially match a predetermined spatial-temporal sequence of locations associated with the content personalized to the user on the HMD, and authenticate the user. 
     In still another example, the processor may generate a display of random content on multiple sequential screens, and may prompt the user to gaze at a location of content personalized to the user in each screen. If a sequence of gaze locations (e.g., a gaze location per screen) matches predetermined locations of the content personalized to the user in the sequence of screen, the user may be authenticated. 
     In yet another example, steps of the method  300  may be performed in a different order. The processor may generate a display of random content of the HMD, may receive information associated with the gaze location of the eye of the user from the eye tracking system, and may associate a content displayed at a given location on the HMD with the gaze location. The processor may then determine if the content displayed at the given location includes content associated with the user or personalized to the user and may authenticate the user accordingly. 
     In still another example, the processor may generate a display of random words on the HMD. Table 1 shows an example of such display or random words. Table 1 shows five columns and five rows, but other arrangements are also possible. In Table 1, column 1 includes adjectives, column 2 includes plural nouns, column 3 includes verbs, column 4 includes adverbs, and column 5 includes adjectives are shown for illustration only. Other word types may be used. In some example, pictures, numbers, symbols, or icons may be used. The wearable computing system and the user may set a predetermined sentence for authenticating the user. For example: “Green tomatoes taste very good.” To authenticate the user, the processor may generate a display such as Table 1, and the user may trace the words that compose the sentence with the eyes of the user. The processor may receive information associated with gaze locations of the eye of the user and may determine whether the sequence of gaze locations substantially matches a predetermined spatial sequence of locations associated with words of the predetermined sentence. The wearable computing system may accordingly authenticate the user. The predetermined sentence may not be grammatically coherent. Any sequence of words, symbols, pictures, numbers, etc., can be set by the wearable computing system and the user. As a number of items included in a table such as Table 1 may increase, combinations of possible sentences may increase. For example, for Table 1, there are 5̂5 (i.e. 3,125) possible sentences. For a seven column five rows table, the number of combinations of possible sentences is 7̂5 (i.e. 16,807). A large number of combinations of sentences or sequences of items may preclude other users or automated systems from guessing or identifying the sentence set by the wearable computing system and the user for authentication. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
            
               
                   
                 Green 
                 Tomatoes 
                 Look 
                 Very 
                 Good 
               
               
                   
                 Red 
                 Aliens 
                 Taste 
                 Really 
                 Bad 
               
               
                   
                 Orange 
                 Shoes 
                 Smell 
                 Quite 
                 Funny 
               
               
                   
                 Small 
                 Flowers 
                 Feel 
                 A bit 
                 Odd 
               
               
                   
                 Old 
                 Dogs 
                 Sound 
                 Mildly 
                 Sad 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 5  is a flow chart illustrating another example method  500  to authenticate a user using eye tracking information.  FIG. 6  is a diagram illustrating the example method  500  to authenticate a user using eye tracking information depicted in  FIG. 5 , in accordance with at least some embodiments of the present disclosure.  FIGS. 5 and 6  will be described together. 
     Method  500  also starts with the wearable computing system including the HMD operating in a locked mode of operation after a period of inactivity by the user. 
     At block  502 , method  500  includes generate a display of a plurality of moving objects. The user may attempt to activate the wearable computing system after the period of inactivity. A processor coupled to the wearable computing system may generate the display of the plurality of moving objects on the HMD. The display of the plurality of moving objects may be randomly generated by the processor. For example, a random display generated by the processor may comprise different object shapes or colors and a different path of motion for each object of the plurality of moving objects. The processor may render paths of the plurality of moving objects on the HMD. 
       FIG. 6  illustrates the HMD integrated into eyeglasses.  FIG. 6  shows the right side of the eyeglasses for illustration. However, the method  500  may apply to both left and right sides. The HMD integrated into the eyeglasses in  FIG. 6  may, for example, be the HMD described in  FIG. 2 . 
     In  FIG. 6 , on a display of the optical system  216 , the processor of the wearable computing system may generate the display of the plurality of moving objects such as a triangle moving through a path  602 , a bird moving through a path  604 , and a star moving through a path  606 , for example. Different shapes and colors may be used. These three shapes are used in describing method  500  as an illustration. A unique characteristic may be associated with each of the plurality of moving objects that may distinguish each moving object from other moving objects. For example, a moving object may have a different shape or a different color that distinguishes the moving object from other moving objects. In another example, rendered paths  602 ,  604 , and  606  may have different distinguishing colors. 
     The processor may display the triangle, bird, and star moving at speeds that may match an ability of a human eye to follow moving objects without saccades. Saccades include rapid eye movement that may disturb the eye tracking system  230 , or cause the eye tracking system  230  to determine a path of eye movement with less accuracy. In another example, the processor may display the plurality of moving objects at any speed and the eye tracking system  230  may not be disturbed. 
     In some examples, eyes may not look at a scene in fixed steadiness; instead, the eyes may move around to locate interesting parts of the scene and may build up a mental three-dimensional map corresponding to the scene. One reason for saccadic movement of an eye may be that a central part of the retina—known as the fovea—plays a role in resolving objects. By moving the eye so that small parts of the scene can be sensed with greater resolution, body resources can be used more efficiently. Eye saccades may be fast if the eye is attempting to follow an object that is moving with a speed that exceeds a certain predetermined speed. Once saccades start, fast eye movement may not be altered or stopped. Saccades may take 200 milliseconds (ms) to initiate, and then may last from 20-200 ms, depending on amplitude of the saccades (e.g., 20-30 ms is typical in language reading). Saccades may disturb or hinder an ability of the eye tracking system  230  to track eye movement. To prevent such disturbance to the eye tracking system  230 , the processor may generate the display of the moving object such that the speed of the moving object may be below a predetermined threshold speed. If the speed exceeds the predetermined threshold speed, saccades may be stimulated. Consequently, the eye tracking system  230  may be disturbed and a performance of the eye tracking system  230  may deteriorate. In this case, the eye tracking system may not be able to accurately track eye movement or eye pupil movement of the user of the wearable computing system. 
     At block  504 , method  500  includes receive information associated with eye movement. For example, in  FIG. 4 , the eye tracking system  230  may track eye movement of the eye  214  of the user. The eye tracking system  230  may, for example, track movements of the eye pupil  404 . As the eye  214  or eye pupil  404  moves, the eye tracking system  230  may track a path associated with the eye  214  or the eye pupil  404  movement. The processor coupled to the wearable computing system may receive the information associated with the path associated with the eye movement from the eye tracking system  230 . 
     At decision block  506 , method  500  may determine whether a path associated with the eye movement substantially matches a path of a moving object with a predetermined characteristic. To authenticate the user of the HMD, the user or the wearable computing system may set a predetermined characteristic that may distinguish a moving object of the plurality of moving objects over other objects of the plurality of moving objects. The moving object may include a picture associated with the user, for example. The predetermined characteristic may include a shape or color associated with the moving object or a color of a rendered path of the moving object. For example, the predetermined characteristic may include a shape of a bird. Thus, for the user to be authenticated, an eye or both eyes of the user may track a path associated with a moving bird on the HMD and may ignore paths of other moving objects. Based on the information associated with the eye movement, the processor may, for example, compare the path associated with the eye movement to the path  604  associated with the moving object with the predetermined characteristic (i.e., the moving bird) generated by the processor as depicted in  FIG. 6 . The predetermined characteristic may also include a direction of motion associated with the moving object. For example, the processor may generate a display of four moving objects; each moving object moving in a different direction (e.g., North, East, South, and West). The predetermined characteristic may be set by the wearable computer system to be one of four directions, e.g., East. For the user to be authenticated, the user may track a moving object moving to the East and ignore other moving objects, for example. In yet another example, the predetermined characteristic may include a size of the moving object. 
     In some examples, the processor may adjust the path associated with the eye movement of the user before comparing the path associated with the eye movement to the path  604  of the moving bird. As described in method  300 , the processor may apply a transform to the path associated with the eye movement to compensate for a difference in a relative location of a gaze axis associated with an eye of the user with respect to a reference axis associated with the HMD. The transform may, for example, include an offset of the path associated with the eye movement to compensate for a shift in the gaze axis of the eye of the user with respect to the reference axis associated with the HMD. The transform may comprise a rotational adjustment to compensate for a rotation in the gaze axis of the eye of the user of the HMD with respect to the reference axis associated with the HMD. The transform may further comprise a scale factor that may compensate for a distance between a camera, coupled to the eye tracking system, monitoring the eye movement of the wearer, or a reference point on the HMD, and the eye of the wearer. As a position of the camera or the reference point changes (e.g., farther or closer to the eye of the wearer) the scale factor may compensate for the change in position of the camera or the reference point with respect to the eye of the wearer. 
     At block  508 , method  500  includes authenticate the user. If the path associated with the eye movement or eye pupil movement of the user matches or substantially matches the path  604  of the moving object with the predetermined characteristic, possibly after adjusting the path associated with the eye movement, the wearable computing system may authenticate the user and switch to be in an unlocked mode of operation. The unlocked mode of operation may comprise unlocking the display screen of the HMD and may comprise increasing a functionality of the wearable computing system. 
     If the path associated with the eye movement or eye pupil movement of the user does not match or does not substantially match the path  604  of the moving object with the predetermined characteristic, the wearable computing system may remain in the locked mode of operation. 
       FIG. 7  is a functional block diagram illustrating an example computing device  700  used in a computing system that is arranged in accordance with at least some embodiments described herein. The computing device may be a personal computer, mobile device, cellular phone, video game system, or global positioning system, and may be implemented as a client device, a server, a system, a combination thereof, or as a portion of components described in  FIGS. 1 ,  2 , and  4 . In a basic configuration  702 , computing device  700  may include one or more processors  710  and system memory  720 . A memory bus  730  can be used for communicating between the processor  710  and the system memory  720 . Depending on the desired configuration, processor  710  can be of any type including but not limited to a microprocessor (μP), a microcontroller (μC), a digital signal processor (DSP), or any combination thereof. A memory controller  715  can also be used with the processor  710 , or in some implementations, the memory controller  715  can be an internal part of the processor  710 . 
     Depending on the desired configuration, the system memory  720  can be of any type including but not limited to volatile memory (such as RAM), non-volatile memory (such as ROM, flash memory, etc.) or any combination thereof. System memory  720  may include one or more applications  722 , and program data  724 . Application  722  may include user authentication algorithm  723  that is arranged to provide inputs to the electronic circuits, in accordance with the present disclosure. Program Data  724  may include content information  725  that could be directed to any number of types of data. In some example embodiments, application  722  can be arranged to operate with program data  724  on an operating system. 
     Computing device  700  can have additional features or functionality, and additional interfaces to facilitate communications between the basic configuration  702  and any devices and interfaces. For example, data storage devices  740  can be provided including removable storage devices  742 , non-removable storage devices  744 , or a combination thereof. Examples of removable storage and non-removable storage devices include magnetic disk devices such as flexible disk drives and hard-disk drives (HDD), optical disk drives such as compact disk (CD) drives or digital versatile disk (DVD) drives, solid state drives (SSD), and tape drives to name a few. Computer storage media can include volatile and nonvolatile, non-transitory, 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. 
     System memory  720  and storage devices  740  are examples of computer storage media. Computer storage media 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, or any other medium which can be used to store the desired information and which can be accessed by computing device  700 . Any such computer storage media can be part of device  700 . 
     Computing device  700  can also include output interfaces  750  that may include a graphics processing unit  752 , which can be configured to communicate to various external devices such as display devices  760  or speakers via one or more A/V ports  754  or a communication interface  770 . The communication interface  770  may include a network controller  772 , which can be arranged to facilitate communications with one or more other computing devices  780  and one or more sensors  782  over a network communication via one or more communication ports  774 . The one or more sensors  782  are shown external to the computing device  500 , but may also be internal to the device. The communication connection is one example of a communication media. Communication media may be embodied by computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave or other transport mechanism, and includes any information delivery media. A modulated data signal can be a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media can include wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency (RF), infrared (IR) and other wireless media. 
     Computing device  700  can be implemented as a portion of a small-form factor portable (or mobile) electronic device such as a cell phone, a personal data assistant (PDA), a personal media player device, a wireless web-watch device, a personal headset device, an application specific device, or a hybrid device that include any of the above functions. Computing device  700  can also be implemented as a personal computer including both laptop computer and non-laptop computer configurations. 
     In some embodiments, the disclosed methods may be implemented as computer program instructions encoded on a computer-readable storage media in a machine-readable format, or on other non-transitory media or articles of manufacture.  FIG. 8  is a schematic illustrating a conceptual partial view of an example computer program product  800  that includes a computer program for executing a computer process on a computing device, arranged according to at least some embodiments presented herein. In one embodiment, the example computer program product  800  is provided using a signal bearing medium  801 . The signal bearing medium  801  may include one or more program instructions  802  that, when executed by one or more processors may provide functionality or portions of the functionality described above with respect to  FIGS. 1-7 . Thus, for example, referring to the embodiments shown in  FIGS. 3 and 5 , one or more features of blocks  302 - 310  and/or blocks  502 - 508  may be undertaken by one or more instructions associated with the signal bearing medium  801 . In addition, the program instructions  802  in  FIG. 8  describe example instructions as well. 
     In some examples, the signal bearing medium  801  may encompass a computer-readable medium  803 , such as, but not limited to, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape, memory, etc. In some implementations, the signal bearing medium  801  may encompass a computer recordable medium  804 , such as, but not limited to, memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations, the signal bearing medium  801  may encompass a communications medium  805 , such as, but not limited to, a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link, etc.). Thus, for example, the signal bearing medium  801  may be conveyed by a wireless form of the communications medium  805  (e.g., a wireless communications medium conforming to the IEEE 802.11 standard or other transmission protocol). 
     The one or more programming instructions  802  may be, for example, computer executable and/or logic implemented instructions. In some examples, a computing device such as the computing device  700  of  FIG. 7  may be configured to provide various operations, functions, or actions in response to the programming instructions  802  conveyed to the computing device  700  by one or more of the computer readable medium  803 , the computer recordable medium  804 , and/or the communications medium  805 . It should be understood that arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g. machines, interfaces, functions, orders, and groupings of functions, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.