PATENT DOCUMENT

Publication Number: US-11874958-B2
Application Number: US-202117448873-A
Country: US
Kind Code: B2

Title: Eye detection methods and devices

Abstract:
A head-mounted device having a plurality of electrodes configured to detect optical events such as the movement of one or more eyes or coarse eye gestures is disclosed. In some examples, the one or more electrodes can be coupled to dielectric elastomer materials whose shape can be changed to vary contact between a user of the head-mounted device and the one or more electrodes to ensure sufficient contact and electrode signal quality. In some examples, the one or more electrodes can be coupled to pressure sensors and control circuitry to monitor and adjust the applied pressure. In some examples, the optical events can be used as triggers for operating the device, including transitioning between operational power modes. In some examples, the triggers can invoke higher resolution sensing capabilities of the head-mounted device. In some examples, the electrodes can be used as an on-head detector to wake-up and/or unlock the device.

Claims:
The invention claimed is: 
     
       1. A device for detecting eye movement, comprising:
 sensing circuitry configured to sense a physiological signal from a plurality of electrodes, the physiological signal associated with the eye movement; and 
 a processor communicatively coupled to the sensing circuitry and programmed for:
 in accordance with the physiological signal meeting one or more first criteria indicative of a first level of eye movement, operating the sensing circuitry in a first power level mode of operation to sense the physiological signal from the plurality of electrodes; 
 in accordance with the physiological signal meeting one or more second criteria indicative of a second level of eye movement, operating the sensing circuitry in a second power level mode of operation to sense the physiological signal from the plurality of electrodes, the second power level mode of operation different than the first power level mode of operation; and 
 while operating the sensing circuitry in the second power level mode of operation:
 in accordance with the physiological signal meeting one or more third criteria, operating the sensing circuitry and the processor in a third mode of operation, the third mode different than the first power level mode of operation and the second power level mode of operation. 
 
 
 
     
     
       2. The device of  claim 1 , wherein:
 the first power level mode of operation comprises operating one or more analog-to-digital converters at a first resolution; and 
 the second power level mode of operation comprises operating the one or more analog-to-digital converters at a second resolution, the second resolution higher than the first resolution. 
 
     
     
       3. The device of  claim 1 , wherein the one or more first criteria comprise comparing an energy level of the physiological signal against a threshold amount of energy. 
     
     
       4. The device of  claim 1 , wherein the one or more first criteria are associated with a blink. 
     
     
       5. The device of  claim 1 , wherein the one or more first criteria are associated with a fixation of gaze. 
     
     
       6. The device of  claim 1 , wherein the one or more first criteria include a determination, via the sensing circuitry, that a user of the device is wearing the device. 
     
     
       7. The device of  claim 1 , wherein the physiological signal comprises an electrooculography (EOG) signal. 
     
     
       8. The device of  claim 1 , further comprising:
 one or more cameras configured to detect ocular events; and 
 operating in the third mode of operation further comprises using the one or more cameras to collect information associated with the physiological signal. 
 
     
     
       9. A method for detecting eye movement, comprising:
 at a device including sensing circuitry and a processor:
 sensing a physiological signal from a plurality of electrodes, the physiological signal associated with the eye movement; 
 
 in accordance with the physiological signal meeting one or more first criteria indicative of a first level of eye movement, operating the sensing circuitry in a first power level mode of operation to sense the physiological signal from the plurality of electrodes; 
 in accordance with the physiological signal meeting one or more second criteria indicative of a second level of eye movement, operating the sensing circuitry in a second power level mode of operation to sense the physiological signal from the plurality of electrodes, the second power level mode of operation different than the first power level mode of operation; and 
 while operating the sensing circuitry in the second power level mode of operation:
 in accordance with the physiological signal meeting one or more third criteria, operating the sensing circuitry and the processor in a third mode of operation, the third mode different than the first power level mode of operation and the second power level mode of operation. 
 
 
     
     
       10. The method of  claim 9 , wherein:
 the first power level mode of operation comprises operating one or more analog-to-digital converters at a first resolution; and 
 the second power level mode of operation comprises operating the one or more analog-to-digital converters at a second resolution, the second resolution higher than the first resolution. 
 
     
     
       11. The method of  claim 9 , wherein the one or more first criteria comprise comparing an energy level of the physiological signal against a threshold amount of energy. 
     
     
       12. The method of  claim 9 , wherein the one or more first criteria are associated with a blink. 
     
     
       13. The method of  claim 9 , wherein the one or more first criteria are associated with a fixation of gaze. 
     
     
       14. The method of  claim 9 , wherein the one or more first criteria include determining that a user of the device is wearing the device. 
     
     
       15. The method of  claim 9 , wherein the physiological signal comprises an electrooculography (EOG) or an electroencephalography (EEG) signal. 
     
     
       16. The method of  claim 9 , wherein operating in the third mode of operation further comprises using one or more cameras to collect information associated with the physiological signal. 
     
     
       17. A non-transitory computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a device including sensing circuitry and one or more processors, cause the device to:
 sense a physiological signal from a plurality of electrodes, the physiological signal associated with eye movement; 
 in accordance with the physiological signal meeting one or more first criteria indicative of a first level of eye movement, operate the sensing circuitry in a first power level mode of operation to sense the physiological signal from the plurality of electrodes; 
 in accordance with the physiological signal meeting one or more second criteria indicative of a second level of eye movement, operate the sensing circuitry in a second power level mode of operation to sense the physiological signal from the plurality of electrodes, the second power level mode of operation different than the first power level mode of operation; and 
 while operating the sensing circuitry in the second power level mode of operation:
 in accordance with the physiological signal meeting one or more third criteria, operating the sensing circuitry and the one or more processors in a third mode of operation, the third mode different than the first power level mode of operation and the second power level mode of operation. 
 
 
     
     
       18. The non-transitory computer readable storage medium of  claim 17 , wherein:
 the first power level mode of operation comprises operating one or more analog-to-digital converters at a first resolution; and 
 the second power level mode of operation comprises operating the one or more analog-to-digital converters at a second resolution, the second resolution higher than the first resolution. 
 
     
     
       19. The non-transitory computer readable storage medium of  claim 17 , wherein the physiological signal comprises an electrooculography (EOG) or an electroencephalography (EEG) signal.

Description:
FIELD OF THE DISCLOSURE 
     This relates generally to methods and devices configured for the detection of eye movement. 
     BACKGROUND OF THE DISCLOSURE 
     Some devices provide eye tracking systems to enable human-computer interaction. In some uses, a device can capture the eye movement of a user, using the movement as an intuitive input for operating and invoking features of the device, allowing faster and more efficient interaction. Devices that decrease friction of interactions between a user and device are desirable. 
     SUMMARY OF THE DISCLOSURE 
     Some examples of the disclosure are directed to a head-mounted device having a plurality of electrodes configured to detect optical events such as the movement of one or more eyes or coarse eye gestures. In some examples, the one or more electrodes can be coupled to dielectric elastomer materials whose shape can be changed to vary contact between a user of the head-mounted device and the one or more electrodes to ensure sufficient contact and electrode signal quality. In some examples, the one or more electrodes can be coupled to pressure sensors and control circuitry to monitor and adjust the applied pressure. In some examples, the optical events can be used as triggers for operating the device, including transitioning between operational power modes. In some examples, the triggers can invoke higher resolution sensing capabilities of the head-mounted device. In some examples, the electrodes can be used as an on-head detector to wake-up and/or unlock the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a symbolic hardware diagram of a system for detecting ocular events according to some embodiments of the disclosure. 
         FIG.  2    illustrates a functional block diagram of a system for detecting ocular events according to some embodiments of the disclosure. 
         FIG.  3    illustrates a plurality of electrodes at locations around the face and head of a user for detecting ocular events according to examples of the disclosure. 
         FIG.  4    illustrates an example electrode configuration comprising a pogo pin element to improve coupling between the electrode and tissue according to examples of the disclosure. 
         FIG.  5 A  illustrates an example electrode configuration including one or more elements in an inactive state, but which can be activated to improve coupling between the electrodes and tissue according to examples of the disclosure. 
         FIG.  5 B  illustrates the example electrode configuration of  FIG.  5 A  including one or more elements in an activated state to improve coupling between the electrodes and tissue according to examples of the disclosure. 
         FIG.  6 A  illustrates an example electrode configuration including one or more elements in an inactive state, but which can be activated to improve coupling between the electrodes and tissue, and additionally a pressure sensor co-located with the electrodes according to examples of the disclosure. 
         FIG.  6 B  illustrates the example electrode and pressure sensor configuration of  FIG.  6 A  in an activated state to improve coupling between the electrodes and tissue according to examples of the disclosure. 
         FIG.  6 C  illustrates a feedback control system for regulating the amount of pressure that electrodes apply to tissue according to some examples of the disclosure. 
         FIG.  7    illustrates exemplary signal processing of electrode signals according to some embodiments of the disclosure. 
         FIG.  8    illustrates exemplary electrodes and an analog front end for processing of electrode signals according to some embodiments of the disclosure. 
         FIG.  9    shows examples of sensor data associated with a head-mounted device according to some examples of the disclosure. 
         FIG.  10    illustrates a method of reduced power consumption eye tracking according to some examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the disclosed examples. 
     As computer input technology continues to develop, various advances in input devices have allowed users to interact with computational systems more efficiently. Head-mounted devices including elements configured to detect movement of eyes are one example of an innovation that can further improve the speed, efficiency, and ease with which users can interact with one or more computational systems. In some embodiments, the gaze of a user can be detected to seamlessly invoke functions of the device. For example, while a user&#39;s hands are otherwise occupied, one or more ocular events (e.g., eye blinks, eye focus, and/or the movement of (eye) gaze) can be monitored to wake-up and/or unlock the device. Gaze estimation can also be used for eye gesture recognition and to provide inputs to various user interfaces, such as to select or switch between settings, and to provide input shortcuts. Additionally or alternatively, focus and/or movement of gaze can serve as a trigger to transition the device and/or systems from a lower power operating mode to a higher power operating mode to reduce computational complexity and prolong battery life of the device. As referred to herein, an ocular event can comprise one or more blinks, fixations and/or saccades of the eyes. It is further understood that ocular events can comprise a sequence of one or more ocular events (e.g., a sequence of one or more blinks, fixations, and/or saccades in some combination). Other use cases for the detection of ocular events includes on head device recognition (e.g., sense that the device is being worn on a user&#39;s head and turn on the device), accessibility for the disabled, and eye health. 
     In some embodiments, a head-mounted device can comprise electrodes configured to monitor electrical impulses corresponding to an ocular event. For example, electrodes coupled to dielectric elastomer (DE) materials can be arranged around features of the body including, but not limited to, in contact with and/or above the nose, behind and/or around the ears, the temples, and/or any other location suitable for detecting and capturing the electrical impulses associated with one or more ocular events or other brain related events and neural activities. 
       FIG.  1    illustrates a symbolic hardware diagram of system  100  for detecting ocular events according to some embodiments of the disclosure. In some embodiments, system  100  can include a portable device  102 , which can be a wearable device such as glasses, goggles, a visor, a mask, a helmet, or other head-mounted device. In some embodiments, device  102  can be communicatively coupled to device  104 , which can be a smart phone, a tablet computer, a laptop computer, an auxiliary device in communication with another device, a wearable host device, etc. In some embodiments, device  102  can additionally or alternatively be communicatively coupled to one or more devices  106 , which can be accessory devices such as a wand, handheld touch controllers, gloves, etc. In some embodiments, system  100  can comprise only a single device  102  (and optional accessory devices  106 ), with the functionality of device  104  included in device  102 . 
     In some embodiments, a plurality of electrodes and associated circuitry (not shown) can be located on or within device  102  such that when the device is worn on a user&#39;s head, the electrodes make contact with selected areas of the user&#39;s head around the eyes, nose, temples and/or ears. Voltage differences between the electrodes can be measured to detect electrical impulses associated with one or more ocular events, such as the movement of a user&#39;s gaze (the location at which the user&#39;s eyes are focused). When the user&#39;s gaze is correlated to a specific area or object within a computer-generated environment or the physical environment, or correlated to a specific user interface affordance within the computer-generated environment, particular operations can be initiated. In various embodiments, the computer-generated environment can be presented on a display or surface within device  102  (e.g., on glasses or a head-mounted device) or device  104  (e.g., on a display of a computing device). 
       FIG.  2    illustrates a functional block diagram of system  200  for detecting ocular events according to some embodiments of the disclosure. In some embodiments, system  200  can be at least partially incorporated into a portable device  202 , which can be wearable device such as glasses, goggles, a visor, a mask, a helmet, or other head-mounted device. A plurality of electrodes  208  can be located on device  202  for detecting electrical impulses associated with one or more ocular events. These electrical impulses can be detected by measuring voltage differences between electrodes using receivers  216 , and can be converted to digital signals via analog-to-digital converter (ADC)  220 . In some embodiments, a plurality of elastomers  210  can be attached to electrodes  208  to assist the electrodes in making better contact with the skin of a user. In one example, drivers  212  can apply stimulation voltages (e.g., a DC, AC, and/or some combination thereof) to elastomers  210 , which can cause the elastomers to deform in response to applied electric fields and cause electrodes  208  to apply increased pressure to the skin of the user. In some embodiments, pressure sensors  214  can be employed in the vicinity of electrodes  208  to detect the pressure being applied to the skin of the user. Electrical signals from pressure sensors  214  can be received by receivers  218  and converted to digital signals via ADC  222 . Controller  226  can be coupled to the one or more ADCs  220  and  222  to receive and/or process the digitized signals from electrodes  208  and pressure sensors  214 . Pressure information received from pressure sensors  214  can be processed by controller  226  to determine updated voltages to be applied by drivers  212 . In this manner, a feedback loop can be created to maintain proper pressure of electrodes  208  against the user. 
     In some embodiments, drivers  212 , receivers  216  and  218 , ADCs  220  and  222 , and controller  226  can constitute an analog front end (AFE)  224  for elastomers  210 , electrodes  208  and pressure sensors  214 , and can be incorporated partially or entirely into a single package (e.g., within an integrated circuit and/or system-on-chip). However, the embodiments described with respect to the front-end circuitry are merely exemplary and not limiting in any way. For example, the above-described components do not necessarily require a single package. In some embodiments, controller  226  can be coupled to one or more wireless communication modules  228  (e.g., a Bluetooth Low Energy radio module, Zigbee module) configured to facilitate transmission and/or reception of signals. Communication modules  228  can be additionally coupled to one or more antennas  230  and one or more power sources such as battery  290 . In some embodiments, the above-described components can be incorporated partially or entirely into a single package (e.g., within an integrated circuit and/or system-on-chip). 
     In some embodiments, device  202  can be communicatively coupled to device  204 , which can be a smart phone, a tablet computer, a laptop computer, an auxiliary device in communication with another device, a wearable host device, etc. that is separate from device  202 . However, in other embodiments, the functionality of device  204  as shown in  FIG.  2    can be included in a single device  202 . Communication circuitry  232  in device  204  can optionally include circuitry for communicating with electronic devices such as device  202 , networks such as the Internet, intranets, a wired network and/or a wireless network, cellular networks and wireless local area networks (LANs). Communication circuitry  232  can also optionally include circuitry for communicating using near-field communication (NFC) and/or short-range communication, such as Bluetooth®. 
     Device  204  can optionally include various sensors  234  (e.g., hand tracking sensors, location sensors, image sensors, touch-sensitive surfaces, motion and/or orientation sensors, eye tracking sensors, microphones or other audio sensors, etc.), one or more display generation components such as display  236 , one or more processors  238 , one or more memories  240 , input devices  242 , and other components. One or more communication buses not shown in  FIG.  2    can optionally be used for communication between the above mentioned components within device  204 . 
     Processors  238  can optionally include one or more general purpose processors, one or more graphics processors, and/or one or more digital signal processors (DSPs). In some embodiments, memory  240  can be a non-transitory computer-readable storage medium (e.g., flash memory, random access memory, or other volatile or non-volatile memory or storage) that stores computer-readable instructions configured to be executed by processors  238  to perform the techniques, processes, and/or methods described herein. In some embodiments, memory  240  can include a non-transitory computer-readable storage medium. A non-transitory computer-readable storage medium can be any medium (e.g., excluding a signal) that can tangibly contain or store computer-executable instructions for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer-readable storage medium can include, but is not limited to, magnetic, optical, and/or semiconductor storage. Examples of such storage include magnetic disks, optical discs based on CD, DVD, or Blu-ray technologies, as well as persistent solid-state memory such as flash, solid-state drives, and the like. 
     Display  236  can optionally include a single display (e.g., a liquid-crystal display (LCD), organic light-emitting diode (OLED), or other types of display). In some embodiments, display  236  can include multiple displays. In some embodiments, display  236  can include a display with a touch-sensitive surface (e.g., a touch screen), a projector, a holographic projector, a retinal projector, etc. 
     In some embodiments, sensors  234  can include a touch-sensitive surface configured to receive user inputs (touch and/or proximity inputs), such as tap inputs and swipe inputs or other gestures. In some embodiments, display  236  and the touch-sensitive surface together can form a touch-sensitive display (e.g., a touch screen integrated with device  204  or external to device  204  that is in communication with device  204 ). Device  204  can also optionally include and receive input from one or more input devices  242  other than a touch-sensitive surface, such as a physical keyboard, a mouse, a stylus and/or a joystick (or any other suitable input device). 
     Sensors  234  can also include image sensors, which can optionally include one or more visible light image sensors, such as charged coupled device (CCD) sensors, and/or complementary metal-oxide-semiconductor (CMOS) sensors operable to obtain images of physical objects from the real-world environment. The image sensors can optionally include one or more infrared (IR) or near infrared (NIR) sensors, such as a passive or an active IR or NIR sensor, for detecting infrared or near infrared light from the real-world environment. For example, an active IR sensor can include an IR emitter for emitting infrared light into the real-world environment. The image sensors can optionally include one or more cameras configured to capture movement of physical objects in the real-world environment. The image sensors can optionally include one or more depth sensors configured to detect the distance of physical objects from device  204 . In some embodiments, information from one or more depth sensors can allow the device to identify and differentiate objects in the real-world environment from other objects in the real-world environment. In some embodiments, one or more depth sensors can allow the device to determine the texture and/or topography of objects in the real-world environment. 
     In some embodiments, device  204  can use CCD sensors, event cameras, and depth sensors in combination to detect the physical environment around the device. In some embodiments, image sensors can include a first image sensor and a second image sensor. The first image sensor and the second image sensor can work together and optionally can be configured to capture different information of physical objects in the real-world environment. In some embodiments, the first image sensor can be a visible light image sensor and the second image sensor can be a depth sensor. In some embodiments, device  204  can use image sensors to detect the position and orientation of device  204  and/or display  236  in the real-world environment. For example, device  204  can use image sensors to track the position and orientation of display  236  relative to one or more fixed objects in the real-world environment. In some embodiments, sensors such as cameras (e.g., image sensors) can be used to capture images of the real-world environment. The images can be processed by processing circuitry (one or more of processor(s)  238 ) to localize and measure light sources. In some embodiments, light can be determined from the reflections and or shadows cast by light sources in the environment. In some embodiments, deep learning (e.g., supervised) or other artificial intelligence or machine learning is used to estimate the lighting characteristic based on input image(s). 
     In some embodiments, sensors  234  can optionally include hand tracking sensors and/or eye tracking sensors. Hand tracking sensors can be configured to track the position/location of a user&#39;s hands and/or fingers, and/or motions of the user&#39;s hands and/or fingers with respect to the computer-generated environment, relative to display  236 , and/or relative to another coordinate system. The eye tracking sensors (different from electrodes  208  that can also be used for eye tracking) can be configured to track the position and movement of a user&#39;s gaze (eyes, face, or head, more generally) with respect to the real-world or computer-generated environment and/or relative to display  236 . The user&#39;s gaze can include a direction in which the eyes are directed, and optionally intersection with a particular point or region of space and/or intersection with a particular object. In some embodiments, the hand tracking sensors and/or the eye tracking sensors can be implemented together with display  236  (e.g., in the same device). In some embodiments, the hand tracking sensors and/or the eye tracking sensors can be implemented separate from display  236  (e.g., in a different device). 
     In some embodiments, the hand tracking sensors can use image sensors (e.g., one or more IR cameras, 3D cameras, depth cameras, etc.) that capture three-dimensional information from the real-world including one or more hands. In some examples, the hands can be resolved with sufficient resolution to distinguish fingers and their respective positions. In some embodiments, one or more image sensors can be positioned relative to the user to define a field of view of the image sensors and an interaction space in which finger/hand position, orientation and/or movement captured by the image sensors are used as inputs (e.g., to distinguish from a user&#39;s resting hand or other hands of other persons in the real-world environment). Tracking the fingers/hands for input (e.g., gestures) can be advantageous in that it provides an input means that does not require the user to touch or hold input device, and using image sensors allows for tracking without requiring the user to wear a beacon or sensor, etc. on the hands/fingers. 
     In some embodiments, the eye tracking sensors can include one or more eye tracking cameras (e.g., IR cameras) and/or illumination sources (e.g., IR light sources/LEDs) that emit light towards a user&#39;s eyes. Eye tracking cameras may be pointed towards a user&#39;s eyes to receive reflected light from the light sources directly or indirectly from the eyes. In some embodiments, both eyes are tracked separately by respective eye tracking cameras and illumination sources, and gaze can be determined from tracking both eyes. In some embodiments, one eye (e.g., a dominant eye) is tracked by a respective eye tracking camera/illumination source. 
     Device  204  can optionally include microphones or other audio sensors. Device  204  can use microphones to detect sound from the user and/or the real-world environment of the user. In some embodiments, the microphones can include an array of microphones that optionally operate together (e.g., to identify ambient noise or to locate the source of sound in space of the real-world environment). In some embodiments, audio and/or voice inputs can be used to interact with the user interface or computer-generated environment captured using one or more audio sensors (e.g., microphones), as permitted by the user of the electronic device. 
     Device  204  can optionally include location sensors configured to detect a location of device  204  and/or display  236 . For example, location sensors can optionally include a GPS receiver that receives data from one or more satellites and allows device  204  to determine the device&#39;s absolute position in the physical world. Device  204  can also optionally include motion and/or orientation sensors configured to detect orientation and/or movement of device  204  and/or display  236 . For example, device  204  can use orientation sensors to track changes in the position and/or orientation of device  204  and/or display  236  (e.g., with respect to physical objects in the real-world environment). Orientation sensors can optionally include one or more gyroscopes, one or more accelerometers, and/or one or more inertial measurement units (IMUs). 
     Device  204  or system  200  can support a variety of applications that may be displayed in the computer-generated environment, such as one or more of the following: a drawing application, a presentation application, a word processing application, a website creation application, a disk authoring application, a spreadsheet application, a gaming application, a telephone application, a video conferencing application, an e-mail application, an instant messaging application, a workout support application, a photo/video management application, a digital camera application, a digital video camera application, a web browsing application, a digital music player application, a television channel browsing application, and/or a digital video player application. 
     A computer-generated environment may be displayed using one or both of devices  202  and  204 , including using one or more display generation components. The computer-generated environment can optionally include various graphical user interfaces (“GUIs”) and/or user interface objects. As described herein, a computer-generated environment including various GUIs may be displayed using device  202  or device  204 , including one or more display generation components. The computer-generated environment can include one or more GUIs associated with an application. For example, a computer-generated environment can display a menu or selectable options to cause launching or display of user interfaces for applications in the computer-generated environment. Similarly, the computer-generated environment can display a menu or selectable options to perform operations with respect to applications that are running in the computer-generated environment. 
     It is understood that the architecture of  FIG.  2    is an example architecture, but that device  202  and device  204  are not limited to the components and configuration of  FIG.  2   . For example, device  202  and  204  can include fewer, additional, or other components in the same or different configurations. 
       FIG.  3    illustrates a plurality of electrodes  304  at locations around the face and head of a user for detecting ocular events according to examples of the disclosure. Although not shown in  FIG.  3   , electrodes  304  can be formed in, coupled to, or otherwise disposed on structures such as glasses in one representative example, and can be formed in, coupled to, or otherwise disposed on the housing of different types of head-mounted devices, such as a pair of goggles, glasses, a mask, a helmet, or a visor in other examples. In various examples, the structures or devices can have a form factor allowing the structure or device to rest partially or entirely on the face of a user. In some examples, the structure or device can comprise one or more transparent, or mostly transparent lenses  306 . In some examples, the lenses  306  can be formed from suitable materials selected to optimize durability, visibility, reduce glare, and/or to project or display images/video (e.g., to display a user interface and corresponding elements). In some embodiments, one or more materials can be disposed in part or entirely over the surface of one or more faces of lenses  306  to achieve the aforementioned optical and/or mechanical qualities. 
     In some embodiments, electrodes  304  can act as sensors configured to capture physiological signals associated with one or more ocular events. The use of electrodes  304  can provide a lower cost implementation for performing eye tracking as compared to camera-based systems, for example. Electrodes  304  can have a linear, or nearly linear relationship between a visual angle of an eye and the amplitude of an output signal. By arranging a plurality of electrodes in different positions around the eye, electrodes  304  can extract information about the direction, movement, and/or fixation of the eye for further processing. In some embodiments, the electrodes can be configured as electrooculography (EOG) sensors to provide measures of electrical activity of the eyes. Specifically, EOG sensors can detect voltage differences between the cornea and the retina of an eye and capture EOG signals. For example, EOG sensors can be configured to provide indications of the dipole formed between a cornea and a retina of an eye. Additionally or alternatively, electrodes can be configured as electroencephalography (EEG) sensors that capture EEG signals and provide measures of electrical activity of the brain of a user. Additionally or alternatively, electrodes can be configured as electromyography (EMG) sensors that capture EMG signals and provide measures of electrical activity of muscle and/or tissue associated with the eye. All of these types of sensors can be used to capture and interpret the intent of a wearer of device  300 . 
     Embodiments comprising sensors configured to detect EOG signals (e.g., referred to as EOG sensors) are primarily described herein; however, it is noted that such description is merely exemplary and not limiting in any way. For example, EEG signals, EMG signals, some combination thereof, and/or any suitable physiological electrical signal(s) associated with one or more ocular events can be used in conjunction with and/or in place of one or more EOG sensors where appropriate. Similarly, embodiments describing EEG and/or EMG sensors can be supplemented with and/or replaced by EOG sensors where appropriate. 
     In some embodiments, electrodes  304  can be placed within or on the surface of a structure or the housing of a device, or in some combination thereof. For example, electrodes  304  can be placed such that when the structure or device is worn, substantial contact is made between the electrodes and one or more portions of the user&#39;s head, preferably with exposed skin. In various examples, electrode  304   a  can be configured to make contact with the forehead of the user, electrodes  304   b  and  304   c  can be configured to make contact with opposing sides of the nose bridge of a user, electrodes  304   d  and  304   k  can be configured to make contact with and/or around the ears, electrodes  304   e  and  304   f  can be configured to make contact around the temples of the user, electrodes  304   g  and  304   h  can be configured to make contact around the cheeks of the user, and electrodes  304   i  and  304   j  can be configured to make contact around the eyebrows of the user. 
     In some embodiments, electrodes  304  can be greater and/or fewer in number than shown. For example, device  300  can comprise two electrodes which, when sensed, provide indications of one or more ocular events to the device. Additionally or alternatively, a greater number of electrodes than shown in  FIG.  3    can be introduced to provide additional information about eye movement. 
     It is understood that the disclosure herein regarding the location, form, and function of electrodes is not limiting in any way. In some embodiments, the electrodes can be arranged in different positions, faces of the structure or housing, and assume any appropriate shape and/or size as desired. For example, the location of electrodes can be selected based on the relative distance between a respective electrode one or more (e.g., reference) electrodes. In some embodiments, a reference electrode can be arranged at a sufficient distance from one or more other electrodes (e.g., measured electrodes), in order to increase the magnitude of differential signals between the reference and the one or more electrodes. This can include electrode  304 - a , which can provide a reference that is symmetrical with respect to additional electrodes (e.g., electrode  304   b  and electrode  304   c  can be arranged on opposing faces of a nose bridge, thus being arranged symmetrically with respect to electrode  304   a  for EOG sensing configurations). Additionally or alternatively, one or more reference electrodes can be selected dynamically while operating device  300  to configure appropriate optical event sensing modalities (e.g., EOG, EMG, and/or EEG). Additionally or alternatively, electrode  304   d  and/or electrode  304   k  (e.g., for EEG sensing) can be configured as reference electrodes, such that the reference electrode(s) are located sufficiently far from additional measured electrodes (e.g., electrode  304   b  and  304   c ) to increase the magnitude of a differential signal between a reference and any one of electrodes  304 . For example, a first reference electrode can be connected to a first input of a differential amplifier while a measurement electrode is connected to a second input of the differential amplifier. At the same time, a second reference electrode can be connected to a stimulation signal. The stimulus can be selected to mitigate the effect of unwanted common-mode noise that appears on the differential signal between the first reference electrode and the measured electrode due to the mismatch in both internal and external components in the signal path. Additionally or alternatively, the stimulus can be selected to otherwise mitigate the effect of unwanted noise on sensing and operation of the device. In some embodiments, driving the second reference electrode (e.g., with a driven right leg technique) can improve the rejection of common-mode noise. For example, environmental noise at 60 Hz can be sensed by device  300 , and a controller included in device  300  can comprise circuitry configured to drive the second reference electrode with a stimulus associated with reducing the 60 Hz noise. In some embodiments, the reference electrode can be configured to eliminate one or more signals (broadband noise, narrowband signals, etc.). It is understood that any electrode can be configured to act as a reference electrode. For example, in some embodiments a multiplexer can receive inputs from some or all of the electrodes, and programmably select any one of the received inputs as the reference electrode. In some embodiments, the reference electrode can alternate between different electrode locations, and a set of electrode measurements can be obtained each time the reference electrode is changed to a different location. These multiple sets of electrode measurements can be used in combination, or separately, to optimize signal quality and accuracy, and to obtain data for eye gaze determination. 
     In some embodiments, electrodes  304  can be “dry” electrodes (e.g., with no conductive gel) that provide a discreet, low cost, and practical solution for sensing EOG signals. Conventional wet electrodes utilize one or more materials configured to improve detection of physiological signals; however, the materials (e.g., electrolytic gels) can be uncomfortable and unsuitable outside of clinical applications, and can be more expensive than dry electrodes. Accordingly, when implemented in some devices, electrodes  304  can be formed from one material or a combination of suitable materials to ensure portability, reusability, cleanliness, and comfort while reducing costs. In some embodiments, electrodes  304  can be formed of one or more suitable conductive materials such as steel, copper, carbon, aluminum, copper, gold, silver, tin, pewter, and/or titanium. The electrodes can also comprise a coating (e.g., foam, powder, film, etc.) disposed on one or more surfaces of the electrodes. The materials associated with the electrodes can be selected appropriately to optimize signal quality and impedance between the skin and the electrodes. 
     When sensing EOG signals or other physiological signals, sufficient contact between electrodes and the tissue (e.g., the epidermis) of a user can be crucial to improve signal quality and integrity, and to obtain a predictable impedance presented to drive and/or sensing circuitry of a device. However, contact requirements can present difficulties when designing a device that is adaptable to variances in physical and physiological features of a user and movement introduced by the user (e.g., a user shifting the device intentionally or inadvertently). The human head, for example, can provide a highly variable contact surface including contours and variable surface conditions (including hair, oil, scar tissue, sweat, etc.). Furthermore, the head of a user is frequently in motion and can cause a device to move, potentially affecting electrode contact integrity. Consequently, wearable device solutions—especially for eye gaze and/or detection applications—stand to benefit by including a mechanism to apply variable pressure between electrodes and human tissue. 
     Therefore, in some embodiments, electrodes can be coupled to elements that are configured to improve contact between the electrodes and user tissues. In some embodiments, these elements can apply pressure to an electrode to press, pull, and/or deform the electrode to provide a contact force on one or more surfaces of the electrode before, during, and/or after electrical measurements. Applied force can better mechanically and electrically couple user tissues (e.g., the epidermis) and electrodes, thus optimizing electrical measurements. In some embodiments, the contact force can be applied via a mechanical element. 
       FIG.  4    illustrates an example electrode configuration comprising a pogo pin element to improve coupling between the electrode and tissue according to examples of the disclosure. In some embodiments, device  400  can be configured to measure one or more EOG signals. As described above, it can be advantageous to provide consistent contact between an electrode  404  and tissue  414  such that device  400  can reliably obtain measurements of electrical impulses associated with a user of the device, for example, by providing a stimulus and/or measuring a signal via the electrode. In some embodiments, the device can comprise one or more elements, such as pogo pin  410 , which can be coupled to the electrode to improve contact between one or more surfaces of the electrode and the tissue. In some embodiments, pogo pin  410  and/or electrode  404  can be retained within a housing  412  within the device and spring-biased with respect to the housing. In some embodiments, the tissue  414  can correspond to the skin (e.g., epidermis) of a user of the electrodes. In some embodiments, electrode  404  can be mounted partially or entirely on the surface of the device. As the tissue is brought in contact with the electrode, the pogo pin can be compressed, thus applying force on the electrode towards the tissue, and improving the quality of mechanical and/or electrical contact. 
       FIG.  5 A  illustrates an example electrode configuration including one or more elements in an inactive state, but which can be activated to improve coupling between the electrodes  504  and tissue  514  according to examples of the disclosure.  FIG.  5 A  illustrates an exemplary device  500  comprising a housing  508 , two electrodes  504 A and  504 B formed in or on the device housing (although other electrodes can also be present in or on the device), and one or more elastomer (elastic polymer) materials  516  (e.g., a dielectric elastomer material). In some examples, elastomer  516  can be sandwiched between electrodes  504 A and  504 B. In some examples, device  500  can include circuitry  518  to drive electrodes  504 A and  504 B. Driving the electrodes  504  can change the shape of the elastomer  516  and cause the electrodes to conform and make contact with tissue  514  (e.g., epidermis) of a user. Although not shown in  FIG.  5 A , electrodes  504  and elastomer  516  can also be arranged in other suitable configurations. For example, the electrodes  504 A and  504 B can be arranged some distance apart within the same plane, or nearly the same plane. Elastomer  516  can be arranged in a different plane from the electrodes such that an electric field (e.g., caused by different voltages applied to electrodes  504 A and  504 B) can alter the shape of the elastomer, in some instances even when portions of the surfaces of the elastomer are uncoupled with respect to portions of the electrodes. In some embodiments, elastomer  516  can be formed from an electroactive material including, but not limited to, dielectric elastomers. Dielectric elastomers can provide a compressive stress in response to an applied electrical field, and can provide numerous benefits in an EOG sensing system, especially when incorporated into designs requiring rugged, lightweight, and comfortable solutions. Dielectric elastomers can exhibit high flexibility/deformation in the presence of an applied electric field, but can return to an initial form in the absence or reduction of the electric field. Dielectric elastomers can include acrylics, silicones, polyurethanes, fluroelastomers, ethylene-propylene rubbers, and/or any other suitable material that can undergo large and reversible deformation in response to electric fields. Dielectric elastomers, as referred to herein, will be used to describe a family of suitable electroactive materials; however, it is understood that such descriptions and embodiments herein are merely exemplary and not limiting in any way. 
       FIG.  5 B  illustrates the example electrode configuration of  FIG.  5 A  including one or more elements in an activated state to improve coupling between the electrodes  504  and tissue  514  according to examples of the disclosure. In  FIG.  5 B , circuitry  518  (e.g., a source) applies a voltage or current across a first electrode  504 A and a second electrode  504 B. In response to the application of voltage and/or current, an electric field is created between first electrode  504 A and second electrode  504 B. In response to this applied electric field, the resulting electrostatic pressure and mechanical compression causes the elastomer  516  located between the first electrode  504 A and the second electrode  504 B to undergo a deformation (as compared to  FIG.  5 A , which is prior to deformation), where the elastomer contracts in thickness and expands in area. Because the first electrode  504 A and the second electrode  504 B are coupled to elastomer  516 , the increase in surface area of the elastomer causes the electrodes to warp or “buckle” and protrude from device housing  508 , resulting in increased force or pressure being applied by the electrodes against tissue  514 . In some embodiments, elastomer  516  is configured as a planar, or nearly planar film that can protrude outside the dimensions of a plane parallel to the film. In some embodiments, elastomer  516  can be implemented as a plurality of layers of dielectric elastomer materials. A plurality of layers of dielectric elastomers allows for creating complex shapes that conform to allow better contact and/or increase the surface area of contact of the electrode with the tissue. The number of layers will depend on the location of the electrodes around areas of the face where there are higher variabilities between users (e.g. cheekbones, eyebrows, etc.). 
       FIG.  6 A  illustrates an example electrode configuration including one or more elements in an inactive state, but which can be activated to improve coupling between the electrodes  604  and tissue  614 , and additionally a pressure sensor  622  co-located with the electrodes according to examples of the disclosure.  FIG.  6 A  is similar to  FIGS.  5 A and  5 B , except for the addition of pressure sensor  622  and associated electronics. In some embodiments, each electrode pair of device  600  can be coupled to one or more respective pressure sensors  622 . Pressure sensors  622  can be coupled to the surface and/or integrated into electrodes  604 A and/or  604 B, and can furnish controller  620  with signals and/or data associated with the force applied to tissue  614  by the electrodes. In some embodiments, each electrode of device  600  can be coupled to one or more respective pressure sensors (e.g., one electrode or a grid of electrodes). Wearable devices such as head mounted devices including one or more pressure sensors can therefore moderate the pressure exerted by electrodes  604  and balance the need to establish and maintain contact between the electrodes and tissue  614 , on the one hand, with the comfort of the user on the other hand. 
       FIG.  6 B  illustrates the example electrode and pressure sensor configuration of  FIG.  6 A  in an activated state to improve coupling between the electrodes  604  and tissue  614  according to examples of the disclosure. In the example of  FIG.  6 B , circuitry (e.g., a source) within controller  620  applies a voltage or current across first electrode  604 A and second electrode  604 B. In response to the application of voltage and/or current, an electric field is created between first electrode  604 A and second electrode  604 B. In response to this applied electric field, the resulting electrostatic pressure and mechanical compression causes the elastomer  616  located between the first electrode  604 A and the second electrode  604 B to undergo a deformation (as compared to  FIG.  6 A , which is prior to deformation), wherein the elastomer contracts in thickness and expands in area. Because the first electrode  604 A and the second electrode  604 B are coupled to elastomer  616 , the increase in surface area of the elastomer causes the electrodes to warp or “buckle” and protrude from device housing  608 . The electrodes  604  and/or the elastomer  616  make contact with tissue  614 , which can correspond to the tissues of a user such as the epidermis. 
     Because pressure sensor  622  is co-located with electrodes  604 , when the electrodes make contact with tissue  614 , the pressure sensor can detect the pressure applied by the electrodes against the tissue. Device  600  can include control circuitry within controller  620  that is coupled to pressure sensor  622  to capture and process pressure readings from the pressure sensor. In some examples, pressure sensor  622  may be selectively monitored rather than continuously monitored. For example, nose/ear electrodes can detect the presence of brain signals or other signals indicative of user activity (e.g., by detecting EEG and/or EOG signals). Upon detecting user activity, other electrodes (e.g., around the eye area) can be activated, and pressure sensor circuitry can also be activated. When pressure sensing is activated, pressure sensor  622  can furnish controller  620  with signals and/or data associated with the force applied to tissue  614  by the electrodes  604 . In some embodiments, each electrode of device  600  can be coupled to one or more respective pressure sensors (e.g., one electrode or a grid of electrodes). 
       FIG.  6 C  illustrates a feedback control system  648  for regulating the amount of pressure that electrodes  604  apply to tissue  614  according to some examples of the disclosure. Feedback control system  648  can ensure that electrodes  604  apply sufficient pressure to tissue  614  to obtain accurate electrode signals, while maintaining relative limits of applied pressure to ensure that a user is not subject to an excess amount of mechanical force while the device attempts to optimize contact. In some embodiments, relevant pressure sensor data can be used as part of a closed loop feedback control system  648  associated with device  600 . Feedback control system  648  can include pressure sensor(s)  622 , comparator  652 , driver circuit  654 , and elastomer  616 . In the embodiment of  FIG.  6 B , actual pressure  660 , applied between electrodes  604  and tissue  614 , can be detected by pressure sensor(s)  622 . Pressure signals  650  from pressure sensor  622  can be fed back to comparator  652 , which can determine the difference between a desired pressure P 0  and actual pressure  660  and generate a difference signal  656 . Desired pressure P 0  can be a predetermined pressure level that is expected to provide electrode signal quality sufficient for accurate eye gaze determination. Difference signal  656  can be fed into driver circuit  654 , which can generate voltage signals  658  to electrodes  604 , which in turn can cause a change in the deformation of elastomer  616  and a change in actual pressure  660 . If difference signal  656  indicates that actual pressure  660  is less than the desired pressure P 0 , driver circuit  654  can modify voltages  658  applied to electrodes  604  to further bend or deform elastomer  616  and increase the actual pressure  660 . After one or more iterations, feedback control system  648  can increase the actual pressure  660  until it reaches an achieved pressure P that is approximately equal to the desired pressure P 0 . However, if difference signal  656  indicates that actual pressure  660  is greater than the desired pressure P 0 , driver circuit  654  can modify voltages  658  applied to electrodes  604  to decrease the bend or deformation of elastomer  616  and reduce the actual pressure  660  until it reaches the desired pressure P 0 . Feedback control system  648  can also ensure that actual pressure  660  is not great enough to subject the user to an excess amount of mechanical force while the device attempts to optimize contact. In some embodiments, control algorithms associated with the closed loop feedback system can be run locally. Additionally or alternatively, control algorithms can be run partially or entirely by a device communicatively coupled to device  600  (e.g., using a wireless communication channel). Additionally or alternatively, pressure data can be monitored in conjunction with and/or instead of other characteristics relevant for EOG sensing, including, but not limited to, the impedance of one or more portions of sensing circuitry, the signal to noise ratio of received signals, and data associated with motion of the device and/or its constituent components. 
     For example, instead of pressure sensor(s)  622 , the impedance of the contact between the electrodes  604  and skin/tissue  614  can be estimated, and the current applied to dielectric polymer  616  (e.g., a current signal) can be changed, as needed, until a sufficient impedance is achieved. Impedance measurements can be obtained via circuitry also used to interface with electrodes. For example, device  600  can comprise one or more current sources configured to supply current to the body of a user. The voltage and current measured via electrodes  604  can be used to calculate an impedance associated with sensing EOG signals. Specifically, the impedance can be indicative of the quality of contact between the tissue  614  and electrodes  604 . 
     When sufficient electrode contact is made with user tissue to generate accurate electrode signals, electrode data can be collected and processed to perform gaze detection and eye tracking. Gaze detection and eye tracking can be utilized as user inputs to trigger various functions. Additionally or alternatively, other triggers to transition between operating modes can be implemented. For example, the trigger can involve an ocular event comprising detection of the gaze of a user. Specifically, the ocular event can comprise fixating on a pre-determined area including, but not limited to, the corners of the user&#39;s field of view, referred to herein as a “hot corner.” The hot corner can also be configured based on the absolute and/or relative dimensions of the device. To accommodate variance in the physical features of potential users, for example, the hot corner can correspond to detecting gaze fixation at a position on or in a lens (e.g., corresponding to a corner of lens  306  of  FIG.  3   ). Additionally or alternatively, the hot corners can be determined in part or entirely based on a determination of the relative angle of the user&#39;s eye. In some embodiments, a first ocular event (e.g., gazing towards a hot corner) can be detected at a first resolution, and after detecting the ocular event (e.g., after a threshold amount of time), one or more further ocular events can be detected at a higher resolution. This embodiment can allow the system to capture broad, general ocular events, and in response to some condition (e.g., a threshold amount of time, a sequence of one or more fixations on one or more locations, and/or detecting one or more blinks), capture finer and more accurate changes associated with one or more ocular events. 
     In some embodiments, a plurality of electrodes can be configured to detect EOG signals, the signals associated with movement of the eye that can be mapped to a defined coordinate system. In some embodiments, electrodes can be configured to create a two-dimensional coordinate map to interpret eye movement. In some examples, the two-dimensional coordinate map can relate to rotation of the eye (e.g., towards the coronal plane bisecting the head of a user). For example, the eyes of a user staring straight ahead can correspond to an initial position, such as a vector extending orthogonally (e.g., in the Z direction) to an imaginary coronal plane (e.g., an X-Y two-dimensional plane) bisecting the user&#39;s head. In some embodiments, the electrodes can provide a linear, or nearly linear, relationship between rotation of the eye (e.g., vertical and horizontal rotation, or a combination thereof) and the voltage output by the electrodes. Accordingly, an exemplary device can detect one or more voltages from the electrodes and compute a perceived rotation of the eye into processed signals (e.g., signals indicative of vertical and horizontal rotation, or a combination thereof). In some embodiments, the rotation of the eye away from the initial position can be calculated using the one or more processed signals and a vector can be calculated corresponding to eye movement. In some examples, the vector can be projected onto the imaginary coronal plane to better correlate vertical and/or horizontal movement of the eye to vertical and/or horizontal navigation of a user interface. 
     An example use case of the above described behavior can be unlocking the device  600  of a user in response to an ocular event. Unlocking the device  600  can include providing user access to one or more functions and/or operating modes of the device. For example, device  600  can be maintained in a low-power mode, even when mounted on the head of a user, until after the ocular event is detected. 
     In response to detecting that the device  600  is being worn by the user, the device can optionally activate functions of one or more components to improve detection of an ocular event, but the device state can appear mostly or completely unchanged from the perspective of the user. In this operating mode, device functionality can be partially enabled. After optionally entering the more fully enabled mode, the user can optionally be prompted to direct their gaze towards a position. The user gaze and/or movement can, in some embodiments, correspond to an ocular event comprising movement of the eyes from a first direction to a second direction (e.g., movement of the eyes from a left portion of the screen to a right portion of the screen). It is understood that the ocular event described is not limiting and could correspond to any suitable movement, including, but not limited to, linear—or mostly linear—movement of the eyes (e.g., vertically, horizontally, diagonally) or movement of the eyes in a curved and/or irregular path. 
     In some embodiments, device  600  can be configured to detect ocular events using a minimal amount of electrodes (e.g., two electrodes). For example, device  600  can comprise two electrodes configured to detect one or more ocular events. In some embodiments, as few as two electrodes can be implemented to detect wake-up conditions. The wake-up conditions described herein can be combined in multiple combinations. As described herein, the wake-up conditions can include detecting EOG and/or EEG signals corresponding to the user placing device  600  on their head. The wake-up conditions can also additionally or alternatively include detecting directional eye movement, such as unidirectional eye movement. In some embodiments, wake-up conditions can include an ocular event associated with fixation of user gaze on a hot corner. For example, a device comprising at least three electrodes can be configured to detect ocular events corresponding to fixations at particular angles of the eye, thus providing EOG sensor data to device  600  that can optionally be used as a wake-up condition. 
       FIG.  7    illustrates exemplary signal processing of electrode signals according to some embodiments of the disclosure. In some embodiments, electrode signals  766  can correspond direct measurements of electrodes. The voltages corresponding to the electrode signals  766  can be further processed by the head mounted device, such as in AFE  224  of device  202  of  FIG.  2   , and/or by an associated computing system that can optionally be a separate device, such as in device  204  of  FIG.  2   . For example, signals can pass through one or more filters. In some embodiments, the filters can include one or more high-pass filters  762 , one or more bandpass filters (not shown), and/or one or more low-pass filters  764 . The filters can be configured to attenuate noise, mitigate signal drift, prevent aliasing, etc. One or more machine learning algorithms can additionally or alternatively be configured to process the received electrode signals  766 . For example, a convolutional neural network (CNN) based model  768  can be applied to data corresponding to signals  766  to improve characterizations of the horizontal and/or visual angles, blink events, and/or gaze fixation and generate an updated model  770 . The device and/or the associated computing system can be configured to invoke functions, methods, and/or processes associated with the device and/or system including transitioning between operating modes, activating voice-recognition software, etc. 
       FIG.  8    illustrates exemplary electrodes  804  and analog front end  872  for processing of electrode signals according to some embodiments of the disclosure. Active electrode  804 -A and reference electrode  804 -B can be modeled with the example circuit elements shown in  FIG.  8   . In some examples, these electrodes  804  can have a signal amplitude of 50 uV to 3.5 mV, frequency content of 0-40 Hz, and an electrode DC offset of up to ±1 V (which can depend on electrode material and skin contact). In some embodiments, a device can include front-end circuitry  872  to condition and sample signals from these electrodes. For example, the device circuitry can include one or more amplifiers  874  (e.g., programmable gain amplifiers). The inputs of a respective amplifier can be tied to an active electrode and to a reference electrode as shown in  FIG.  8    to obtain a differential voltage at the amplifier output, the output corresponding to the relative voltage difference detected by the active electrode and associated with ocular events. The output of the amplifier  874  can further be coupled to one or more variable analog-to-digital converters (ADCs)  876  that can be configurable to quantize signals at one or more resolutions. A controller  878  can be coupled to the one or more ADCs  876  to receive and/or process the digitized signals. 
     In some embodiments, the analog front-end  872  can include one or more elements to measure impedance. For example, the analog front-end can include one or more current sources configured to stimulate the tissue of a user. Voltages measured (e.g., by the one or more electrodes of the device) in response can then be used in conjunction with the known current to calculate impedance. In some embodiments, the measured impedance can be used by a controller included in the device to configure one or more dielectric elastomers (e.g., to increase and/or decrease pressure between one or more electrodes and tissues of a user). The increased pressure will help achieve a better signal quality by reducing the electrode-skin impedance up to a point that it does not compromise user comfort. 
     The analog front-end circuitry can in some embodiments be configured with particular specifications in mind. For example, the signals received by the one or more amplifiers can span a range including, but not limited to, 50 μV-3.5 mV comprising frequency content including, but not limited to, 0-40 Hz. Additionally or alternatively, the common-mode input range of the amplifiers can include ±1V, and the input impedance can exceed 1 GΩ. 
       FIG.  9    shows examples of EOG sensor data associated with a head-mounted device according to some examples of the disclosure. In some embodiments, a device can comprise a plurality of electrodes configured to detect movement of the eyes. In some embodiments, the electrodes can be arranged to capture EOG signals. As described herein, the electrode configuration is not limited in any way provided that the signals captured by the electrodes are associated with ocular events. For example, the EOG signals output by the electrodes can correspond to a blink of a user. Additionally or alternatively, the strength of the blink can be sensed and detected by the head-mounted device. In some embodiments, one or more electrodes can be arranged to make contact with tissues superior and/or inferior to the eyes of a user. Additionally or alternatively, one or more electrodes can be arranged to make contact with tissues lateral and/or medial to the eyes. In some embodiments, the electrodes can be arranged to make contact with the bridge of the user&#39;s nose (e.g., corresponding to electrodes  304   b  and/or  304   c  of  FIG.  3   ), with the forehead of the user (e.g., corresponding to electrode  304   a ), and/or with areas around and behind the user&#39;s ears (e.g., corresponding to  304   d  and  304   k ). 
     In some embodiments, an electrode in contact with the user&#39;s forehead can be configured as a reference voltage to calculate a plurality of differential voltages indicative of eye gaze and/or movement. For example, signal  932  and signal  934  can correspond to differential voltages between the reference electrode on the user&#39;s forehead (e.g., corresponding to electrode  304   a ) and electrodes on the right and the left of the user&#39;s nose bridge (e.g., corresponding to electrodes  304   b  and  304   c ). Signal  936  and signal  938  can correspond to differential voltages between the reference electrode and electrodes behind/around the right and the left ear of the user (e.g., corresponding to electrodes  304   d  and  304   k ). 
     In some embodiments, the signals shown in  FIG.  9    can correspond to several ocular events. For example, signals  932 ,  934 ,  936  and  938  during time period  940  can correspond to the blink of a user. As described previously, the strength of the blink can also be detected. Blinks can be used to perform functions of the device, such as confirming and/or selecting an element of a user interface associated with the head-mounted device. EOG signals provided by the electrodes can, in some embodiments, correspond to rotation of the eye in one or more directions. For example, events associated with movement of the eyes can correspond to horizontal and/or vertical angles of gaze and can be detected during time period  942 . During time period  942 , signals  932 ,  934 ,  936  and  938  exhibit a downward slope, which can correspond to a change in the visual angle of the eyes including the user gaze shifting upwards. In some embodiments, the EOG signals can also capture the state of the user gaze. Time period  944  can correspond to the user maintaining a particular visual angle (e.g., the visual angle established during time period  942 ). Subsequent changes to visual angles can additionally be detected as shown during time period  946 , which can correspond to the user gaze shifting to the right. In some embodiments, the plateaus, or near plateaus, of signals  932 ,  934 ,  936  and  938  can raise and/or lower as the visual angle of the user gaze changes. Similarly, in some embodiments, the magnitude of the signals  932 ,  934 ,  936  and  938  can vary for each user and as the strength of events vary (e.g., based on the strength of a blink). 
       FIG.  10    illustrates a method of reduced power consumption eye tracking according to some examples of the disclosure. Device power consumption can be particularly critical when integrated power sources are limited, such as in wearable devices comprising finite power sources (e.g., batteries). Moreover, heat generated during operation of electronics can add to discomfort of wearable devices; therefore, reducing power consumed by the device can be a key device and/or system design consideration. In some embodiments, signals captured by electrodes having sufficient contact can be captured and configured to vary operating modes of the device. As described above, the electrodes can be arranged and configured to make contact between one or more of the temples, nose, cheeks, eyebrows, behind the ears, etc. In some embodiments, a subset of the electrodes of the device (e.g., electrodes in contact with the nose and/or one or more ears of the user) can be configured to capture signals corresponding to brain activity of the user. For example, electrical impulses corresponding to movement of the eyes and/or muscles within the user&#39;s face can be detected. Additionally or alternatively, the brain activity associated with the movement of the eyes and/or muscles can be detected. In some embodiments, until the brain activity is sensed (e.g., EEG signals are detected), the device can operate in a low power mode as shown in block  1080 . The low power mode can comprise turning off some or all of components and/or circuitry within and/or associated with the head mounted device. In some embodiments, some or all of the components and/or circuitry can be configured in a sleep mode (e.g., low power consumption). In some embodiments, the low power mode can comprise configuring some or all of the components and/or circuitry associated with the head-mounted device to operate poll registers, communication channels, or other computing and sensing circuitry at a lower rate and/or resolution. In some embodiments, the device can operate in a low power mode until other electrical activity related to one or more ocular events is detected, and the detected electrical activity can be quantified into an energy level (e.g., by integrating electrical activity over time) as shown in block  1082 . While operating in the low power mode, power can be conserved until receiving a trigger (e.g., detecting brain activity and/or ocular events), thus optimizing the lifespan of the device, and minimizing superfluous calculations, computations, and/or measurements aside from those associated with detecting the trigger. In some embodiments, the calculated energy level can be compared against a threshold energy level as shown in block  1082 . If the calculated energy level exceeds the threshold, this can trigger the device to enter a higher power mode. 
     After detecting the trigger, the operating mode can transition from a lower to a higher power mode as shown in block  1084 . For example, one or more analog-to-digital converters (ADCs) can be configured to transition from a first resolution at a lower power condition (block  1080 ) to a second resolution at a higher power condition (block  1084 ), the second resolution finer than the first. In some examples, the trigger can also be associated with enabling the stimulation, measurement, and/or configuration of one or more electrodes of the device. In some embodiments, in response to the trigger, one or more electrodes can transition from a sleeping (i.e., lower power) mode to a higher power mode at which the one or more electrodes can be sensed, polled, and/or detected. Additionally or alternatively, pressure sensors  622  coupled and/or embedded into the electrodes can similarly be configured in response to the trigger. In some embodiments coarse electrode-based eye tracking as shown in block  1086  can be utilized until finer resolution eye tracking is needed, which may depend on the function being performed by the eye tracking and/or the application or user interface being presented. In situations where finer resolution eye tracking is needed, camera-based eye tracking can be utilized, as shown in block  1088 . 
     Therefore, according to the above, some examples of the disclosure are directed to a device for detecting eye movement, comprising sensing circuitry configured to sense a physiological signal, the sensing circuitry including a plurality of electrodes, and one or more elastomer materials coupled to a respective pair of electrodes of the plurality of electrodes, wherein the respective pair of electrodes are configured for receiving a signal associated with altering a shape of the one or more elastomer materials and the respective pair of electrodes to improve contact between at least one of the respective pair of electrodes and tissue of a user. Alternatively or additionally to one or more of the examples above, in some examples the one or more elastomer materials comprise dielectric elastomer materials. Alternatively or additionally to one or more of the examples above, in some examples the device further comprises one or more pressure sensors coupled to at least one electrode in the respective pair of electrodes, and control circuitry coupled to the one or more pressure sensors and the sensing circuitry. Alternatively or additionally to one or more of the examples above, in some examples the signal associated with altering the shape of the one or more elastomer materials is modified based on a first criteria. Alternatively or additionally to one or more of the examples above, in some examples the first criteria comprises meeting a threshold signal-to-noise ratio associated with the physiological signal. Alternatively or additionally to one or more of the examples above, in some examples the first criteria comprises meeting a threshold amount of force detected by the one or more pressure sensors. Alternatively or additionally to one or more of the examples above, in some examples the signal associated with altering the shape of the one or more elastomer materials is modified based on an impedance associated with the physiological signal. Alternatively or additionally to one or more of the examples above, in some examples the device further comprises one or more current sources configured to supply a current to the respective pair of electrodes via the tissues of a user of the device. Alternatively or additionally to one or more of the examples above, in some examples the physiological signal is a differential signal between two respective pairs of electrodes of the plurality of electrodes, wherein a first respective electrode pair of the plurality of electrodes is configured as a reference electrode, and a second respective electrode pair of the plurality of electrodes is configured as an active electrode. Alternatively or additionally to one or more of the examples above, in some examples the device further comprises circuitry configured to detect noise affecting the device, and a third respective electrode of the plurality of electrodes configured to supply a stimulus signal to a user of the device, wherein the stimulus signal is associated with reducing the detected noise. Alternatively or additionally to one or more of the examples above, in some examples the device further comprises one or more amplifiers coupled to the respective pair of electrodes, one or more analog-to-digital converters, wherein a resolution of a respective analog-to-digital converter of the one or more analog-to-digital converters is variable, and communication circuitry communicatively coupled to the processing circuitry and configured to transmit data associated with the physiological signal. Alternatively or additionally to one or more of the examples above, in some examples the physiological signal is associated with one or more ocular events. Alternatively or additionally to one or more of the examples above, in some examples the plurality of electrodes include one or more electrooculography (EOG) sensors. 
     Some examples of the disclosure a directed to a method for detecting eye movement, comprising coupling one or more elastomer materials to a respective pair of electrodes of a plurality of pairs of electrodes, contacting the respective pair of electrodes and the one or more elastomer materials with tissue associated with an eye of a user, receiving a signal at the respective pair of electrodes, altering a shape of the one or more elastomer materials and the coupled respective pair of electrodes based on the received signal to improve contact between the respective pair of electrodes and the tissue of the user, and sensing the physiological signal from the respective pair of electrodes, the physiological signal associated with the eye moment. Alternatively or additionally to one or more of the examples above, in some examples the one or more elastomer materials comprise dielectric elastomer materials. Alternatively or additionally to one or more of the examples above, in some examples the method further comprises altering the shape of the one or more elastomer materials and the coupled respective pair of electrodes based on first criteria. Alternatively or additionally to one or more of the examples above, in some examples the first criteria includes an amount of force applied by the respective pair of electrodes to the tissue of the user. Alternatively or additionally to one or more of the examples above, in some examples the first criteria includes a threshold signal-to-noise ratio associated with the physiological signal. Alternatively or additionally to one or more of the examples above, in some examples the first criteria includes a threshold impedance associated with the physiological signal. Alternatively or additionally to one or more of the examples above, in some examples the respective pair of electrodes includes one or more electrooculography (EOG) sensors. 
     Some examples of the disclosure are directed to a device for detecting eye movement, comprising sensing circuitry configured to sense a physiological signal from a plurality of electrodes, the physiological signal associated with the eye movement, and a processor communicatively coupled to the sensing circuitry and programmed for, in accordance with the physiological signal meeting a first criteria indicative of a first level of eye movement, operating the sensing circuitry in a first power level mode of operation, and in accordance with the physiological signal meeting a second criteria indicative of a second level of eye movement, operating the sensing circuitry in a second power level mode of operation, the second mode different than the first. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first power mode comprises operating the one-or-more analog-to-digital converters at a first resolution, and the second power mode comprises operating the one or more analog-to-digital converters at a second resolution, the second resolution higher than the first. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria comprises comparing an energy level of the physiological signal against a threshold amount of energy. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria is associated with a blink. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria is associated with a fixation of gaze. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria includes a determination, via the sensing circuitry, that a user of the device is wearing the device. Alternatively or additionally to one or more of the examples disclosed above, in some examples the physiological signal comprises an electrooculography (EOG) signal. Alternatively or additionally to one or more of the examples disclosed above, in some examples the processor is further programmed for, while operating the sensing circuitry in the second power level mode of operation, in accordance with the physiological signal meeting a third criteria, operating the sensing circuitry and the processing circuitry in a third mode of operation, the third mode different than the first mode and the second mode. Alternatively or additionally to one or more of the examples disclosed above, in some examples the device further comprises one or more cameras configured to detect ocular events, and operating in the third mode of operation further comprises using the one or more cameras to collect information associated with the physiological signal. 
     Some examples of the disclosure are directed to a method for detecting eye movement, comprising sensing a physiological signal from a plurality of electrodes, the physiological signal associated with the eye moment, in accordance with the physiological signal meeting a first criteria indicative of a first level of eye movement, operating the sensing circuitry in a first power level mode of operation, and in accordance with the physiological signal meeting a second criteria indicative of a second level of eye movement, operating the sensing circuitry in a second power level mode of operation, the second mode different than the first. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first power mode comprises operating one-or-more analog-to-digital converters at a first resolution, and the second power mode comprises operating the one or more analog-to-digital converters at a second resolution, the second resolution higher than the first. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria comprises comparing an energy level of the physiological signal against a threshold amount of energy. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria is associated with a blink. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria is associated with a fixation of gaze. Alternatively or additionally to one or more of the examples disclosed above, in some examples the first criteria includes determining that a user of the device is wearing the device. Alternatively or additionally to one or more of the examples disclosed above, in some examples the physiological signal comprises an electrooculography (EOG) or an electroencephalography (EEG) signal. Alternatively or additionally to one or more of the examples disclosed above, in some examples the method further comprises, while operating the sensing circuitry in the second power level mode of operation, in accordance with the physiological signal meeting a third criteria, operating the sensing circuitry and the processing circuitry in a third mode of operation, the third mode different than the first mode and the second mode. Alternatively or additionally to one or more of the examples disclosed above, in some examples operating in the third mode of operation further comprises using one or more cameras to collect information associated with the physiological signal. 
     Although examples of this disclosure have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of examples of this disclosure as defined by the appended claims.

Metadata:
Filing Date: 20210924
Publication Date: 20240116
Grant Date: 20240116
Priority Date: 20210924
Inventors: AZEMI, ERDRIN
MOIN, Ali
KRAH, CHRISTOPH H.
CHENG, JOSEPH YITAN
DOGRUSOZ, KAAN EMRE
YEKE YAZDANDOOST, MOHAMMAD
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/013", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/3203", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/325", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/015", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/017", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3206", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/3234", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/3287", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/325", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/013", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/3287", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/013", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/017", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/015", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/015", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3203", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/3206", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/3234", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/3287", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/017", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/325", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 85477412