Patent Publication Number: US-9886116-B2

Title: Gesture and touch input detection through force sensing

Description:
TECHNICAL FIELD 
     The present invention relates generally to computing devices, and more specifically, to detecting inputs for computing devices. 
     BACKGROUND 
     Many types of input devices may be used to provide input to computing devices, such as buttons or keys, mice, trackballs, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation. Typically touch screens can include a touch sensor panel, which may be a clear panel with a touch-sensitive surface, and a display device that can be positioned behind the panel so that the touch-sensitive surface substantially covers the viewable area of the display device. Touch screens allow a user to provide various types of input to the computing device by touching the touch sensor panel using a finger, stylus, or other object at a location dictated by a user interface being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event. 
     Touch sensor panels can be formed from a matrix of row and column traces, with sensors or pixels present where the rows and columns cross over each other while being separated by a dielectric material. Each row can be driven by a stimulation signal, and touch locations can be identified through changes in the stimulation signal. Typically, a touch location is sensed based on an interference of the stimulation signal, such that a touch location may correspond to a location where the stimulation signal is the weakest. Touch sensor panels may generally be configured to detect touches from a user&#39;s fingers, which generally have a surface area that contacts the touch sensor panel to disturb the stimulation signal sufficiently for touch location to be recognized. 
     In some instances, computing devices incorporating touch screens may be configured to detect one or more gestures as user inputs. For example, a first type of finger movement, such as a user moving two fingers away from each other may indicate a first type of input (e.g., a zoom-in command), whereas a second type of finger movement, such as a user moving two fingers towards each other may indicate a second type of input (e.g., a zoom-out command). However, in some instances, if a user begins a gesture just outside of the touch screen sensing region, such as towards an edge of the device, the gesture may be difficult to detect because only a portion of the gesture may be detected by the touch screen. In these instances, computing devices may sense inputs that may be different from a user&#39;s intended input. 
     SUMMARY 
     One example of the present disclosure may take the form of a computing device configured detect a user input. The computing device includes a processor, a touch interface in communication with the processor and configured to detect a touch signal corresponding to an object approaching or contacting a surface, and at least three force sensors in communication with the processor and configured to detect a force signal corresponding to an object exerting a force on the surface. In response to the force the processor determines a force centroid location and the touch signals are processed by the processor by analyzing the force centroid location. 
     Another example of the disclosure may take the form of a method for detecting user inputs to a computing device through force sensing. The method includes detecting by three or more force sensors a force input, calculating by a processor in communication with the force sensors a force centroid based on the force input, and using the force centroid to analyze one or more user inputs to the computing device. 
     Yet another example of the disclosure may take the form of a mobile computer configured to detect at least two types of user inputs. The mobile computer includes a processor, a touch screen in communication with the processor, and at least three pressure sensors in communication with the processor. The touch screen is configured to detect a touch signal corresponding to a user finger approaching or contacting the touch screen. The at least three pressure sensors are configured to detect a pressure signal corresponding to an object proving pressure on a surface. In response to the pressure signal the processor determines a centroid location relative to the surface and the touch signal is processed by the processor by analyzing the centroid location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a computing device including a touch interface for detecting one or more touch inputs. 
         FIG. 2  is a simplified block diagram of the computing device of  FIG. 1 . 
         FIG. 3  is a simplified cross-section view of the computing device taken along line  3 - 3  in  FIG. 1 . 
         FIG. 4A  is a top plan view of a user providing an input gesture to the computing device. 
         FIG. 4B  is a top plan view of a first force centroid and a second force centroid corresponding to the input gesture of  FIG. 4A . 
         FIG. 4C  is a top plan view illustrating a force centroid location and a touch centroid location based on one or more user inputs. 
         FIG. 5A  is a top perspective view of the computing device of  FIG. 1  being grasped by a user. 
         FIG. 5B  is a top plan view illustrating the force centroid locations based on one or more user inputs. 
         FIG. 6  is a top plan view of the computing device of  FIG. 1  having user input buttons positioned on a non-capacitive touch sensitive surface. 
         FIG. 7  is a flow chart illustrating a method for detecting user inputs and touch gestures using force sensors. 
     
    
    
     SPECIFICATION 
     Overview 
     In some embodiments herein, a computing device including a touch interface for detecting one or more touch inputs and a plurality of force sensors for detecting one or more force inputs is disclosed. The computing device may include at least three, and typically four or more, force sensors that detect a force input on a surface. The force sensors may be distributed along different portions of the computing device, and generally may be operably connected to a cover surface. The cover surface may cover a portion if not all of the touch screen and/or an enclosure, such as a protective glass layer covering the touch screen or other portions of the computing device. The cover surface may extend over the touch screen, as well as other non-touch sensitive portions of the computing device. For example, in some instances the computing device may include a “black mask” portion or other enclosure area of the display that may border a portion, if not all, of the touch screen, but may not be sensitive to capacitive or touch inputs. 
     In some embodiments, the force sensors may be used to detect inputs on non-touch sensitive regions of the computing device. For example, if a user applies a force on the black mask, the force sensors may detect the input force and/or its location. Additionally, the force sensors may be used to enhance detection of inputs on the touch sensitive regions of the computing device. In these embodiments, the force sensors may enhance detection of input gestures that may begin on the non-touch sensitive surface, as well as may provide additional input receiving mechanisms which may allow the non-touch sensitive surfaces of the computing device to receive user inputs. 
     In some instances, when an input force is received, such as due to a user applying a force on the cover glass, the force sensors may each detect a force signal that may correspond to the input force, but the sensed signal may vary based on the location of each of the force sensors. For example, if the input force is exerted on a top right hand corner of the surface, a first force sensor adjacent the top right corner of the surface may sense a first force value, a second force sensor that may be in a left bottom corner may sense a second force value, and a third force sensor in a left top corner may sense a third value. These three force values may be used to determine a location of a center of the force or force centroid location. 
     The force centroid location may be used to analyze one or more touch inputs and/or user force inputs to the computing device. As a first example, the force centroid may be used in conjunction with any detected touch input to determine if a touch input is part of a force gesture that began off of the touch screen sensitive area, such that the touch input may be treated as a touch gesture. As a second example, the force centroid may be used to determine if one or more touch inputs are accidental, such as due to a user holding the computing device and placing a portion of a finger on the touch sensitive screen but not meaning to provide a touch input. As a third example, the force centroid may be used to detect user inputs outside of the touch sensitive area. In this example, the computing device may detect certain user inputs which may be correlated to virtual buttons or commands outside of the touch sensitive or active touch region. 
     DETAILED DESCRIPTION 
     Turning now to the figures, a computing device including a touch screen will now be discussed in more detail.  FIG. 1  is a top perspective view of a computing device  100  including a touch interface  102  and force sensors  110 ,  112 ,  114 ,  116 . The computing device  100  may be substantially any type of electronic device including a touch input mechanism, such as the touch interface  102  or other touch screen and associated components. For example, the computing device  100  may be a laptop computer, a tablet computer, a smart-phone, a digital music player, portable gaming station, or the like. 
     The computing device  100  may include the touch interface  102 , an enclosure  104  at least partially surrounding the touch interface  102 , a cover surface  106  covering at least a portion of the touch interface  102  and/or the enclosure  104 , and/or one or more input buttons  108 . The enclosure  104  encloses one or more components of the computing device  100 , as well as may surround and/or secure a portion of the touch interface  102  to the computing device  100 . The one or more input buttons  108  may provide input functions to the computing device  100 . For example, the input buttons  108  may adjust a volume for the computing device  100 , turn the computing device  100  on or off, or may provide other inputs for the computing device  100 . Further, the computing device  100  may also include one or more receiving ports (not shown). The receiving ports may receive one or more plugs or connectors, such as but not limited to, a universal serial bus (USB) cable, a tip ring sleeve connector, or the like. 
     The cover surface  106  may be incorporated as a portion of the touch interface  102  and/or may be a protective surface that protects the touch interface  102  and/or enclosure  104  or portions thereof. In some embodiments, the cover surface  106  may extend over a top surface of the enclosure  104  as well as a top surface of the touch interface  102 . In these embodiments, the cover surface  106  may also act as an enclosure for the components of the computing device  100 . The cover surface  106  may be a material that may allow for one or more electrical properties to be transmitted therethrough. For example, the cover surface  106  may be a glass or plastic. Additionally, in instances where the touch interface  102  may also include a display screen, at least a portion of the cover surface  106  that extends over the touch interface  102  may be clear or partially transparent. Typically the cover surface  106  should be sufficiently thin to allow for sufficient electrode coupling between the touch interface  102  and any external input objects (e.g., fingers, input devices). 
     The touch interface  102  may include one or more touch sensors in order to detect one or more touch or capacitive inputs, such as due to a user placing his or her finger close to or on the cover surface  106  and/or touch interface  102 . The touch interface  102  will be discussed in more detail below, but may generally be any type of interface configured to detect changes in capacitance or other electrical parameters that may be correlated to a user input. 
     The force sensors  110 ,  112 ,  114 ,  116  are configured to sense an input force, or a change in a sensed force, that may be applied to the cover surface  106 , the enclosure  104 , and/or touch interface  102 . Although the force sensors are discussed herein as receiving an input force that is applied to the cover surface, it should be noted that the force sensors may be operably connected to a variety of different surfaces or elements within the computing device where a user may apply a force. Accordingly, the discussion of any particular embodiments for the force sensors is meant as illustrative only, and not meant as limiting. 
     With continued reference to  FIG. 1 , in one embodiment, the first force sensor  110  may be positioned in a top right corner of the computing device  100 , the second force sensor  112  may be positioned in a top left corner of the computing device  100 , the third force sensor  114  may be positioned in a bottom left corner, and the fourth force sensor  116  may be positioned in a bottom right corner of the computing device  100 . The force sensors  110 ,  112 ,  114 ,  116  may be operably connected to the cover surface  106  and/or touch interface  102  and may detect one or more input forces exerted on either the touch interface  102  or the cover surface  106 . In a specific example, the force sensors  106  may be strain gages that may produce a signal based on or otherwise corresponding to a bending force applied thereto. As another example, the force sensors may be capacitive sensors that may sense changes in capacitance as pressure is applied to the cover surface  106 . As yet another example, the force sensors may include optical sensors. In this example, a small camera or other imaging capture device may capture images of a known pattern that may be included on the bottom of the cover surface  106  and/or touch interface. As pressure is applied to the cover surface  106 , the pattern may be varied (e.g., certain points may move closer to each other or may deform outwards), and the camera may capture the pattern and any changes thereto. The pattern changes could be translated by the computing device into one or more scaled images that may translate into force measurements. 
     In some embodiments, such as shown in  FIG. 1 , the force sensors  110 ,  112 ,  114 ,  116  may be spaced apart from one another along the perimeter of the touch interface  102 , such as in each corner of a rectangular shaped enclosure. However, in other embodiments, the force sensors  110 ,  112 ,  114 ,  116  may be positioned adjacent one another, within the touch interface  102 , above or below the touch interface  102 , or the like. Moreover, although only four force sensors are illustrated, the computing device  100  may include substantially any number of force sensors  102 . That said, in many embodiments, the computing device  100  may include at least three force sensors  102  to better estimate the location of a force centroid, which will be discussed in more detail below. Additionally, the number and positioning of the force sensors may be varied based on changes in the shape, dimensions, or the like of the computing device. 
     The computing device  100  may include one or more components that may be in communication with one another.  FIG. 2  is a simplified block diagram of the computing device  100 . With reference to  FIG. 2 , the computing device  100  may further include a power source  102 , an input/output interface  122 , a processor  124 , one or more memory components  126 , and/or one or more sensors  128 . 
     The processor  124  may be substantially any electronic device cable of processing, receiving, and/or transmitting instructions. For example, the processor  124  may be a microprocessor or a microcomputer. As described herein, the term “processor” is meant to encompass a single processor or processing unit, multiple processors, or multiple processing units, or other suitably configured computing element. For example, select components of the electronic device  100  may be controlled by a first processor and other components of the electronic device  100  may be controlled by a second processor, where the first and second processors may or may not be in communication with each other. As a specific example, the touch interface  102  may include one or more separate processing components that may be in communication with the processor  124 . 
     The memory  126  may store electronic data that may be utilized by the electronic device  100 . For example, the memory  126  may store electrical data or content e.g., audio files, video files, document files, and so on, corresponding to various applications. The memory  126  may be, for example, non-volatile storage, a magnetic storage medium, optical storage medium, magneto-optical storage medium, read only memory, random access memory, erasable programmable memory, flash memory, or a combination of one or more types of memory components. 
     The electronic device  100  may also include one or more sensors  128 , in addition to the force sensors  110 ,  112 ,  114 ,  116  and/or touch sensors incorporated into the touch interface  102 . The sensors  128  may provide substantially any type of input to the electronic device  100 . For example, the sensors  128  may be one or more accelerometers, gyroscopes, light sensors, image sensors (such as a camera), force sensors, and so on. 
     The power source  120  may be substantially any device capable of providing energy to the computing device  100 . For example, the power source  120  may be a battery, a connection cable that may be configured to connect the computing device  100  to another power source such as a wall outlet, or the like. 
     The input/output interface  122  may be configured to provide communication to and from the computing device  100 . For example, the input/output interface  122  may facilitate communication by the computing device to and from a variety of devices/sources. For example, the input/output interface  122  may receive data from user, control buttons on the computing device  100 , and so on. Additionally, the input/output interface  122  may also receive/transmit data to and from an external drive, e.g., a universal serial bus (USB), or other video/audio/data inputs. 
     It should be noted that  FIGS. 1 and 2  are exemplary only. In other examples, the electronic device may include fewer or more components than those shown in  FIGS. 1 and 2 . Additionally, the illustrated electronic device is only an example of a computing device incorporating the touch interface and force sensors. 
     The touch interface  102  and force sensors  110 ,  112 ,  114 ,  116  will now be discussed in more detail.  FIG. 3  is a cross-section view of the computing device  100  taken along line  3 - 3  in  FIG. 1 . With reference to  FIG. 3 , the cover surface  106  may extend over a top surface of the enclosure  104 , as well as over the force sensors  110 ,  112 ,  114 ,  116 , and the touch interface  102 . The force sensors  110 ,  112 ,  114 ,  116  may be operably connected to the cover surface  106 , the enclosure  104 , as well may be in communication with the touch interface  102 . 
     With reference to  FIG. 3 , the touch interface  102  and/or force sensors  110 ,  112 ,  114 ,  116  may be operably connected to and/or in communication with a substrate or circuit board  134 . The substrate  134  may provide communication between the force sensors  110 ,  112 ,  114 ,  116  and/or touch interface  102  with one or more components for the computing device  100 , such as but not limited to, the processor  124 , the memory  126 , and the power source  120 . 
     The touch interface  102  is configured to receive inputs from an object (e.g., location information based on a user&#39;s finger or data from the input device) and to send this information to the processor  124 . The touch interface  102  may report touches to the processor  124  and the processor interprets the touches in accordance with its programming. For example, the processor may initiate a task in accordance with a particular touch. The touch interface  102  may include a display screen  132  and a sensor panel  130  positioned at least partially over the display screen  132 . 
     The display screen  132  is configured to display one or more output images and/or videos for the computing device  100 . The display screen  132  may be substantially any type of display mechanism, such as a liquid crystal display (LCD), plasma display, or the like. In instances where the display screen  132  is a LCD display, the display screen  132  may include (not shown) various layers such a fluorescent panel, one or more polarizing filters, a layer of liquid crystal cells, a color filter, or the like. It should be noted that  FIG. 3  is not drawn to scale and is a schematic view of the touch interface  102 , for instance, there may be a gap (not shown) between on or more components of the touch interface and/or cover surface. 
     In some embodiments, the cover surface  106  may be a clear glass or plastic panel that may allow the display screen  132  to be viewable therethrough. The sensor panel  130  may include one or more electrodes which may be deposited on the cover surface  106 . For example, the electrode layer may include transparent conductive materials and pattern techniques such as ITO and printing. 
     It should be noted that in some embodiments, the touch interface  102  be substantially any type of touch screen or touch detecting component(s). For example, the touch interface may not be see-through and/or may not correspond to a display screen. In these instances, a particular surface or group of surfaces may be configured to receive touch inputs, that may or may not correspond to a separately displayed user interface, icons, or the like. 
     The sensor panel  130  may include one or more touch sensors that may detect changes in an electrical parameter that may correspond to an object touch or approaching the touch interface  102 . For example, the sensor panel  130  may include one or two layers of electrodes which may be spaced apart across the panel  130 . The electrodes may define one or more nodes that act as capacitive coupling sensors to detect touches on the touch interface  102 . The number and configuration of the nodes may be varied, depending on the desired sensitivity of the touch interface  102 . 
     In some embodiments, the sensor panel  130  of the touch interface  102  may be configured to detect touches on the surface of the touch interface  102  by sensing one or more changes in capacitance. Typically when two electrically conductive members come close to one another, without actually touching, their electric fields interact to form a capacitance. As briefly described above, the sensor panel  130  may include a plurality of sensing nodes that may be formed by one or more electrodes that may interact with an external object, such as a user&#39;s finger, to detect the presence of the object. 
     The touch interface  102  can detect changes in capacitance at each node, which may allow the touch interface  102  to determine when and where a user has touched various surfaces of the cover surface  106  and/or touch interface  102  with one or more objects. The touch interface  102  may be substantially any type of touch detecting mechanism as generally known in the art, and the specific implementations may be based on a number of different factors, such as but not limited to, the size of the touch screen, the desired sensitivity of the touch screen, and so on. Accordingly, the discussion of the any particular touch interface configuration is meant as illustrative only and not limiting. 
     With reference again to  FIG. 3 , the force sensors  110 ,  112 ,  114 ,  116  may be operably connected to the cover surface  106  in order to detect input forces that may be applied at substantially any location of the cover surface  106 . For example, the force sensors  110 ,  112 ,  114 ,  116  may measure force by sensing a deflection of the cover surface  106 . However, in other embodiments, the force sensors  110 ,  112 ,  114 ,  116  may be other mechanisms configured to sense a change in one or more parameters that may be correlated to a change in force. 
     The touch interface  102  and the force sensors  110 ,  112 ,  114 ,  116  may be used to determine the location and strength of various inputs to the cover surface  106  of the computing device  100 . The computing device  100 , using the force sensors  110 ,  112 ,  114 ,  116  positioned at each corner of cover surface  106 , may be configured to determine the location of a force centroid for a user input or inputs. The force sensors may be differently configured and/or positioned in other embodiments, but may still be used to determine and assign forces to particular input locations. 
     Centroid Calculations with a Detected Touch Position 
     For user inputs that are in communication with the touch interface  102  (e.g., detectable by the touch interface, such as being within an active touch region), the touch sensors  130  may determine the location of any touches or inputs to cover surface  106  positioned over the touch interface  102 , and the force sensors  110 ,  112 ,  114 ,  116  may determine the force magnitude at locations of the cover surface  106 . 
     For example, in instances where the user provides an input force to the cover surface  106  above the touch interface  102  with a single finger, the computing device  100  may associate that position with the entire force detected by the one or more force sensors  110 ,  112 ,  114 ,  116 . However, in many instances the user may provide an input force or forces with one or more fingers and/or other portions of his or her hand. For example, the touch interface  102  may be used to capture input gestures based on the number or type of finger inputs. In these instances, the computing device  100  may determine an input force associated with several or all of the various touch locations on the cover surface  106  to input force levels. In some embodiments, the computing device  100  may determine a centroid of the overall applied force, which may include a location of approximately a center of the applied forces. In this manner, if there is a force applied by two fingers of a user, the centroid may be positioned between the two fingers. 
     Examples of centroid calculations to determine the force centroid location will be discussed in more detail below. As briefly discussed above, in instances where the input force may be applied to the touch interface  102 , the position of the force may be determined based on the touch location data sensed by the touch interface  102 . In these embodiments, the computing device  100  may determine the touch location providing a majority of the input force using a centroid calculation. However, because in some embodiments the computing device  100  may include only a four force sensors  110 ,  112 ,  114 ,  116 , some calculations and/or estimations may be used to determine the finger that may be providing the input force. As described in more detail below, the computing device  100  may utilize the position information as detected by touch interface  102  along with various force signals detected by the four force sensors  110 ,  112 ,  114 ,  116  to determine the touch location corresponding to a particular force. By determining the centroid of the input forces provided to the cover surface  106 , and due to the position of touches on the cover surface  106  detected by the sensor panel  130  of the touch screen  106 , the computing device  100  may determine the finger providing the input force as the finger closest to the force centroid. The global force centroid C GF  may be expressed by Eq. (1) below: 
     
       
         
           
             
               
                 
                   
                     C 
                     GF 
                   
                   = 
                   
                     
                       ∑ 
                       
                         
                           W 
                           i 
                         
                         ⁢ 
                         
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     In Eq. (1), the global force centroid C GF  is expressed as the sum of a select number of positions Pi multiplied times the weight Wi at each position Pi, divided by the sum of the weights Wi. The positions Pi may be determined by the touch interface  102 . For example, if the user presses on the cover surface  106  with two fingers, those fingers may provide a position input signal (such as a change in capacitance) at two separate locations or nodes. Those locations may be used as two input positions Pi in Eq. (1). In some instances, the positions Pi may be a set or coordinates or a single axis coordinates, in the latter example, Eq. (1) may be repeated twice, once for a X or horizontal axis and once for a Y or vertical axis. In other examples, such as illustrated in Eq. (2), the positions Pi may be represented as position vectors relative to a predetermined origin. The weight Wi may be same as the force sensed by each force sensor, or may be the force sensed by each force sensor multiplied by gravitational acceleration (e,g., 9,80665 m/s 2  or 32.174 ft/s 2 ). 
     Eq. (1) also uses the weight Wi for each position; however, because there may not be force sensors  110 ,  112 ,  114 ,  116  at every location of the cover surface  106  where there may be a touch, the weight Wi at each position may not be known, only the force at the location of the force sensors  110 ,  112 ,  114 ,  116 . In these embodiments, the position information along with the force sensed at each input sensor  110 ,  112 ,  114 ,  116  may be used to solve for a global force centroid. 
     Using the example of a computing device  100  having four force sensors  110 ,  112 ,  114 ,  116 , Eq. (1) may be expanded to include the values for each of the input sensors  110 ,  112 ,  114 ,  116  extrapolated to Eq. (2) below: 
     
       
         
           
             
               
                 
                   
                     
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                     ) 
                   
                 
               
             
           
         
       
     
     In Eq. (2) above and with reference to  FIG. 1 , LPF represents the low pass filter, C RB   F[n]  is the force registered by the right bottom (RB) force sensor  116 , {right arrow over (C)} BL   position  is the position vector from respective sensor to the touch position, C TL   F[n]  represents the force registered by the top left force sensor  110 , {right arrow over (C)} TL   position  is the position vector from respective sensor to the touch position, C RL   F[n]  is the force registered by the right top force sensor  112 , {right arrow over (C)} RL   position  is the position vector from respective sensor to the touch position, C RB   F[n]  is the force registered by the right bottom force sensor  114 , {right arrow over (C)} RB   position  is the position vector from respective sensor to the touch position, which may represent the location and value of particular force relative to a particular predetermined origin. 
     As indicated in Eq. (2) in some embodiments, the values for the force sensors may be low pass filtered prior to processing. This filtering may be used to remove noise, such as spikes within the signal. However, in other instances, the input values from the force sensors  110 ,  112 ,  114 ,  116  may not need to be low pass filtered based on the noise level for each of the signals. As described above, the force sensors  110 ,  112 ,  114 ,  116  may be configured to detect a force at a predetermined location. However, in instances where there may be one or more forces applied to the cover surface  106 , the force registered at each force sensor  110 ,  112 ,  114 ,  116  may be reduced or increased as compared to other sensors  110 ,  112 ,  114 ,  116  based on the distance of the applied force from the respective force sensor  110 ,  112 ,  114 ,  116 . In other words, a moment of the cover surface  106  for a particular force sensor  110 ,  112 ,  114 ,  116  may vary based on distance from the particular force as a moment arm or perpendicular distance from the force location to the force sensor  110 ,  112 ,  114 ,  116  may increase or decrease. In some embodiments, the force sensors  110 ,  112 ,  114 ,  116  may be strain gages, which may register varying force inputs based on the moment, so that the force inputs as sensed by the force sensors  110 ,  112 ,  114 ,  116  may vary based on the distance to a respective input force. 
     Although the above examples were described with respect to four force sensors  110 ,  112 ,  114 ,  116 , in other embodiments, three sensors or more than four sensors may also be used. For example, because only three points are required to define a plane, the computing device  100  may include only three force sensors and use substantially the same calculations as above. Alternatively, the computing device  100  may include more force sensors in order to refine the above calculations. 
     Using Eq. (2) above, the global force centroid, that is the location of the center of the applied force, may be determined. As an example, with a single touch, the center of the force may be determined by analyzing the force registered at each force sensor, along with the location of the touch detected by the touch interface  102 . Because in this example, there is only a single input touch, the computing device  100  may determine that the entire force was provided at the location of the force centroid, and then use that knowledge to determine the force magnitude applied thereto. 
     Centroid Calculations without a Detected Touch Position 
     For user inputs that are not in communication with the touch interface  102 , such as those that are in the black mask  118  portion of the cover surface  106  that is not above the touch interface  102 , or otherwise outside of the touch sensitive region of the touch screen, the force sensors  110 ,  112 ,  116 ,  118  may detect the force magnitude and may extrapolate position from the varying values detected by each sensor  110 ,  112 ,  114 ,  116 . For example, with reference to  FIG. 1 , assuming that a first force F 1  is applied to a portion of the cover surface  106  outside of the touch sensitive region, each of the sensors  110 ,  112 ,  114 ,  116  may sense a different force value (although the total applied input force may be constant) that may correspond to the distance that each force sensor  110 ,  112 ,  114 ,  116  is positioned from the input force F 1 . As shown in  FIG. 1 , the first force sensor  110  may be spaced a distance of D 1  from the input force F 1 , the second force sensor  112  may be spaced a distance of D 2  from the input force F 1 , the third force sensor  114  may be spaced a distance of D 3  from the input force F 1 , and the fourth force sensor  116  may be spaced a distance of D 4  from the input force F 1 . 
     In the example illustrated in  FIG. 1 , the input force F 1  is shown closest to the second sensor  112 , and thus the second force sensor  112  may sense the largest magnitude force. Similarly, the third force sensor  114  may sense the second largest magnitude force, and so on. In this example, the differences in sensed force magnitude may correspond to the difference in distance that each of the force sensors  110 ,  112 ,  114 ,  116  are positioned from the input force F 1 . Because the distance from which each of the sensors  110 ,  112 ,  1146 ,  116  are positioned from each other is known, this known distance may be used along with the varying sensed magnitudes to determine the approximate location of the input force F 1 . 
     As a specific, non-limiting example, the centroid location may be determined by determining the location of an axis centroid along a first axis and a second axis. The axis centroid values may then represent a coordinate for the overall centroid location. In this example, the computing device may use force values as measured by each of the sensors  110 ,  112 ,  114 ,  116  on a given axis of the device  100  (e.g., x or y axis). In some instances the device may include an axis centroid value for each side of the device, e.g., a left y axis, a right y axis, a top x axis, and/or a bottom x axis. Each value for a particular axis may be summed, and then value as detected by each respective sensor (that is, the force sensed by each sensor) may be multiplied by that axis length, providing a location of the axis centroid with respect to the particular axis. Specifically, if the second sensor  112  senses a force of 80 grams and the fourth sensor  114  senses a force of 20 grams, the total force for the left y axis may be 100 grams. In instances where the distance between the second sensor  112  and the fourth sensor  114  is 160 mm, than the force centroid for this example on the left edge y axis may be (80 g/100 g)*160 mm, such that the centroid for this axis is 128 mm from the fourth sensor  114  and 32 mm away from the second sensor  112 . However, it should be noted that the above example is only one manner in which the force centroid may be determined, and other embodiments are envisioned. Moreover, the calculations for a force centroid may be varied based on the number and/or position of the sensors. 
     Using the Force Centroid Location 
     Using the equations listed above, the location of the global force centroid C GF  can be determined for both instances where a touch may be detected by the touch interface  102 , as well as instances where a touch may not be detected by the touch interface  102 . The computing device  100  may then use the location of the C GF  to track changes in applied force in order to better detect gestures that may begin in the black mask  118 .  FIG. 4A  is a top plan view of a user&#39;s finger  140  providing a first force F 1 , the moving across the cover surface  106  to provide a second force F 2 . It should be noted that the two forces F 1  and F 2  may be a substantially continuous force applied along a length L 1  of the movement of the finger  140 , but may indicate the beginning and the end of a user input, such as a gesture. 
     After the user has input the finger gesture, by moving his or her finger  140  from the black mask  118  towards the touch interface  102 , the location of the force centroid may also move.  FIG. 4B  is a top plan view of the computing device  100  of  FIG. 4A  illustrating a first force centroid C GF1  and a second force centroid C GF2  corresponding to the first force F 1  and the second force F 2 , respectively. The two force centroid C GF1  and C GF2  may be determined using the equations above, and as the finger moves  140 , and the force location moves, the global force centroid (that is, the center of the applied forces) may correspondingly move. In this manner the computing device  100  may be able to determine that the finger  140  moved from the black mask  118  towards the touch interface  102 , although the touch interface  102  may not detect a first touch corresponding to the first force, but only a second touch corresponding to the second force F 2 . In this example, when the touch interface  102  finally detects the touch the processor may be able to determine whether a corresponding force centroid originated in the black mask  118  (or other portion outside of the touch interface  102 ) and is now at or close to the second finger. That is, whether the force centroid moved a distance of L 1  that may be correlated to a distance from the second touch position to the black mask  118 . 
     In the example illustrated in  FIGS. 4A and 4B , the force sensors  110 ,  112 ,  114 ,  116  may sense different values for approximately the same level of force based on the distance between the force and a particular force sensor. In other words, for the first force F 1 , the force sensors  110 ,  112  positioned at the top of the cover surface  106  may sense a larger force magnitude as compared to the bottom force sensors  114 ,  116 . In this manner, the processor may use the above provided equations to estimate the force centroid by approximating the location of the touch or by correlating the position of the force based on the different magnitudes detected at each force sensor  110 ,  112 ,  114 ,  116 . An estimate of the location of the force centroid may be sufficient to determine if a user provide input is a gesture and/or whether it began in the black mask  118  because more detailed inputs of the gesture may be detected by the touch interface  102  once they extend across the black mask  118 . 
     In some embodiments, the computing device  100  may determine or estimate a force applied to the black mask or non-touch sensitive portion of the cover surface.  FIG. 4C  is a top plan view illustrating a touch location centroid and force centroid. With reference to  FIG. 4C , the processor may analyze the force centroid in light of a touch centroid location to determine what percentage of the total force sensed by the force sensors  110 ,  112 ,  114 ,  116  may be attributed to touches on the touch interface  102  as opposed to touches on the black mask  118 . The touch location centroid  115  may be the centroid of one or more touches as sensed by the touch interfaces. In other words, if there is a single touch on the touch interface, the touch centroid will be positioned at that touch location, and if there is more than one touch, the touch centroid may be positioned at the centroid between the touches. The force centroid  117 , as discussed in more detail above, may be positioned at the centroid of the sensed forces applied to the cover surface. The force allocation between the touch interface  102  and the black mask  118  may be used to provide inputs to the device  100 , as well as help to evaluate touches as discussed in more detail below. 
     With reference to  FIG. 4C , in instances where the force centroid C GF    117  does not match a computed touch location centroid  115 , the processor may determine that the discrepancy may be due to the fact that a touch was applied in the black mask  118  region. Such a touch likely would not be detected by the touch interface  102 , as it falls outside the touch sensitive region. In other words, if a user provides a force in the black mask, the force sensors may detect the applied force, but the touch interface may not detect the touch location, and thus the touch location would not be incorporated into the touch location centroid. Accordingly, in these instances, the force centroid may be a first position and the touch location centroid  115  may be at a second location, spaced apart from the force centroid  117  location. 
     Using these assumptions, the device  100  may determine the intensity of a force applied in the black mask  118 . Specifically, the location difference between the touch centroid and the force centroid may be used to determine (or at least estimate) the location and intensity of a force applied in the black mask  118  region. For example, the computing device  100  may take into account the known location of the black mask  118 , shown in  FIG. 4C  as being a rectangle surrounding the touch interface  102 . In this example, a line extending from the touch centroid location, through the force centroid, and through the black mask  118  boundary region may be determined. That is, the two centroids may be connected through a line extending between the two, and the line may extend towards the black mask  118  bordering the touch sensitive region. 
     The intersection point  113  of the line as it enters the black mask region  118  may be used as a likely indicator of the location of the force input on the black mask  118 . This may allow the computing device  100  to determine the side of the black mask  118  where the force was applied, as well as a general estimate of the actual location relative to that side of the black mask. Once the intersection  113  location is known, the ratio of the distance between the force centroid and the touch centroid to that location may be used to estimate the percentage of force applied in the touch region versus the black mask region. For instance, the force centroid may be located at a distance L 2  from the intersection point and the touch location centroid may be located at a distance L 1  from the intersection point. The percentage of the total sensed force that may be attributed to the black mask  118  region may be determined to be equal to one minus the ratio of the distance L 2  over the distance L 1 . Expressed as an equation 
     
       
         
           
             
               BlackMaskForce 
               ⁢ 
               
                   
               
               ⁢ 
               % 
             
             = 
             
               
                 ( 
                 
                   1 
                   - 
                   
                     
                       L 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                     
                     
                       L 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                 
                 ) 
               
               × 
               100. 
             
           
         
       
     
     The remaining percentage of the sensed force may then be attributed to the touch interface touch locations. In this manner, the percentage of the total force applied to the cover surface  106  that was applied in the black mask region  118 , as well as the percentage applied in the touch interface  102  region may be determined. 
     The force sensors  110 ,  112 ,  114 ,  116  may also be used to determine whether a user force should be rejected or ignored. In other words, whether a user input on the touch interface  102  may be accidental.  FIG. 5A  is a top perspective view of a user holding the computing device  100  with one hand  144  and applying a force with a finger  140  from a second hand.  FIG. 5B  illustrates the force centroid location due to a touch by a thumb  142 . With reference to  FIGS. 5A and 5B , in some embodiments, users may hold the computing device  100  with one hand  144  while using the second hand to provide touch inputs to the touch interface  102 . In some instances, one or more fingers of the first hand  144 , such as the thumb  142  illustrated in  FIG. 5A , may extend across the black mask  118  onto the touch interface  102 . The placement of the thumb  142  (or other finger) may cause the touch interface  102  to detect a user touch input, although the user may have inadvertently placed the thumb  142  on the touch interface  102 . In other words, although the user may have touched the thumb  142  on the touch interface  102 , he or she may not have wished to provide a touch input to the device  100 . 
     With reference to  FIG. 5A , the thumb  142  may input a first touch T 1  and if the user also uses his or her finger  140  from the second hand, that may be a second touch input T 2 . As a first example, in instances where the user may only touch the touch interface  102  with the thumb  142 , the force sensors  110 ,  112 ,  114 ,  116  may detect a force corresponding only to the first touch T 1 , as well as any additional forces exerted on the black mask  118  due to the other portions of the hand  144 . In this example, the force centroid C GF1  may be located on the black mask  118  or adjacent to the black mask  118  on the touch interface  102 . In other words, because the hand  144  may also apply some force to the cover surface  106  (as it grips the device  100 ), the force centroid may be positioned at a location between the first touch T 1  of the thumb  142  and the position of the hand  144 . In this example, the processor may determine that the first touch T 1  is inadvertent, as the force centroid is not located at the touch position T 1 , but closer towards or on the black mask  118  portion of the cover surface  106 . Thus, using the location of the centroid C GF1  the processor may determine that the touch T 1  is inadvertent, as most of the force is centered away from the touch towards or on the black mask  118 . 
     In one embodiment, with reference to  FIG. 5B , the computing device  100  may set a boundary  148  around the touch T 1  and if the force centroid C GF1  is not within the boundary  148 , the touch T 1  may be rejected and not processed as an input. In these embodiments, the boundary  148  may be set to be wider for touches closer towards a center of the touch interface  102  and may be smaller for touches closer to the black mask  118  or the edge of the touch interface  102 . This may provide a greater sensitivity of the device  100  to reject touch inputs that may be accidental. 
     As a second example, with reference again to  FIGS. 5A and 5B , in some instances, the user may provide a second touch T 2  with the finger  140  from a second hand. In this example, in instances where the second touch T 2  may be purposeful, the force centroid may move towards the second touch as the user may apply a stronger force than the resting force of the thumb  142 . Specifically, C GF2  may represent the location of the second force centroid that may correspond to the average center of the forces applied by the finger  140  and the thumb  142 . In this case, because the second force centroid C GF2  may be located approximately adjacent the second touch T 2  within the second boundary  150  and outside of the boundary  148  around the first touch T 1 , the first touch T 1  may be rejected. 
     It should be noted that in some instances a user may provide a purposeful input with both the finger  140  and the thumb  142  (or a second finger). In these instances, the force centroid may be positioned outside of the two boundaries  148 ,  150  and thus the processor  124  may interpret both touches as purposeful. This is because the total magnitude of the input forces may be relatively evenly distributed between both the finger  140  and the thumb  142  which may indicate that the user was applying a relatively equal force by both the finger  140  and thumb  142 , and thus meant to provide an input to the touch interface  102  with both. 
     In some instances, the computing device  100  may include one or more buttons within the black mask  118  or other non-touch sensitive portions of the cover surface  106 .  FIG. 6  is a top plan view of the computing device  100  including two buttons  152 ,  154  positioned on the black mask  118  outside of the touch sensitive region. In this example, a first button  152  may correspond to a first command and a second button  154  may correspond to a second command. For example, the first button  152  may correspond to a next page command and the second button  154  may correspond to a previous page command. The buttons may be differently configured based on the computing device  100  and/or applications operating on the computing device  100 . 
     In the embodiment illustrated in  FIG. 6  the buttons may be virtual in that they may not include a mechanical switch, but may be selected based on the location of the force centroid. In other words, a specific button  152 ,  154  may be determined to be selected by a user if the force centroid is closer towards a particular button. 
     Similarly, the computing device  100  may use the force sensors  110 ,  112 ,  114 ,  116  to detect taps on the black mask  118 . The taps, such as a user pressing on the black mask  118  with his or her finger, may be used as an input to the computing device  100 . For example, a first tap may represent a first command, whereas two taps successively may represent a second command. Additionally, the computing device  100  may detect gestures by a user outside of the touch sensitive region. For example, as a user slides his or her finger along a portion of the black mask  118  the force centroid may move correspondingly, and this motion may be sensed by the force sensors  110 ,  112 ,  114 ,  116  and tracked as a change in the location of the force centroid, and provided as a particular input. In this example, the sliding gesture may be used to switch pages on a reading application, adjust a volume, adjust brightness, and so on. Additionally, in these embodiments, these type of gestures may be distinguished from gestures that ultimately terminate in the touch sensitive region, as these type of gestures may not be correlated to any touch inputs. That is, gestures in the non-touch region, such as the black mask  118 , may not include a corresponding touch input on the touch interface  102 . 
     A method for using the force sensors  110 ,  112 ,  114 ,  116  to detect one or more force inputs to the computing device  100  will now be discussed.  FIG. 7  is a flow chart illustrating an method  200  for using the force sensors of the computing device  100 . The method  200  may begin with operation  202  and the force sensors  110 ,  112 ,  114 ,  116  may detect an input force. For example, as the user presses against the cover surface  106 , an input force may be detected by the force sensors  110 ,  112 ,  114 ,  116 . 
     Once the input force is detected, the method may proceed to operation  204  and the processor  124  may determine the location of the force centroid for the applied force of forces. In some embodiments, the sensed inputs for each of the force sensors  110 ,  112 ,  114 ,  116  may be used to determine the force centroid location. In instances where the input force may be applied to a touch sensitive region, the position of the input forces may be determined by the touch interface  102 , and using the position information and force information the force centroid may be determined. However, for input forces not on the touch sensitive region, the sensed magnitudes by each of the force sensors  110 ,  112 ,  114 ,  116  may be used to determine the location of the force centroid. 
     As, during, or after the force centroid is determined, the method  200  may proceed to operation  206  and the computing device  100  may determine whether there was also a capacitive input. In other words, the computing device  100  may determine whether there was a touch input sensed in addition to the force input. In some embodiments, the touch determination may be done simultaneously with operation  204 , as the touch information may be used (in some instances) to determine the force centroid location. In instances where the force input may be provided on the black mask  118 , or another area outside of the sensitive region of the touch interface  102 , the computing device  100  may determine that there is no capacitive input. On the contrary, if the user has provided an input to the touch sensitive area of the device  100 , such as on the touch interface  102 , the computing device  100  may detect a capacitive input (such as a change in capacitance due to a user&#39;s finger interacting with the touch sensors  130 ). 
     If a capacitive input is not detected, the method  200  may proceed to operation  214 , which will be discussed in more detail. If a capacitive input is detected, the method  200  may proceed to operation  208  and the computing device  100 , specifically the processor  124 , may determine whether the centroid is within the boundary. For example, with reference to  FIG. 5B , the boundaries  148 ,  150  may surround each of the touches and may extend around the touch location a predetermined distance. 
     If the centroid is not within the boundary, the method  200  may proceed to operation  210 . As discussed above with respect to  FIGS. 5A and 5B , when the centroid is outside of the touch boundary  148 ,  150 , the method  200  may proceed to operation  210  and the touch input may be rejected. For example, as shown in  FIGS. 5A and 5B , the touch may be due to the thumb  142  and thus may be determined to be inadvertent if it is outside the boundary surrounding the touch. If the centroid is within the boundary, the method  200  may proceed to operation  208 , which will be discussed in more detail below. 
     With continued reference to  FIG. 7 , after operation  210  and the capacitive touch is rejected or otherwise not processed, the method  200  may proceed to operation  214 . In operation  214 , the processor  124  may determine whether the centroid location corresponds to a button location and/or whether the movement corresponds to a command, such as a gesture. For example, with reference to  FIG. 6 , the computing device  100  may include a number of buttons within the black mask  118  which may be determined to be selected with the force centroid has a location approximately equal to the location of the button or other predefined area. 
     If the centroid location does not correspond to a button location or a gesture, the method  200  may proceed to optional operation  218 . In operation  218 , the computing device  100  may store the force input information, such as the centroid location in one or more of the memory components. In these embodiments, the stored information may be used at a later time, such as if there is a subsequent touch in the touch interface  120  region that may have begun with an input force in the black mask  118 . However, in other embodiments, the force information may not be stored. 
     However, if the centroid location corresponds to a button or gesture, the method  200  may proceed to operation  216  and the processor  124  may process the button or gesture. This may include providing the input to an application running, or otherwise utilizing the force inputs. After operations  216  and  218 , the method  200  may proceed to an end state  224 . 
     As briefly discussed above, in operation  208  if the centroid is within the boundary, the method  200  may proceed to operation  212 . In operation  212  the computing device  100  may determine whether the centroid has moved. For example, in instances where a user may be performing a touch gesture, the centroid may have moved from the black mask  118  to the touch interface  102  region as the user completed the gesture. Centroid movement may be determined by analyzing one or more previous centroid locations based on one or more previous force inputs. 
     If the centroid has moved, the method  2000  may proceed to operation  222 . In operation  222  the processor  124  may analyze the touch inputs detected by the touch interface  102  through the touch sensors  130 , as well as the centroid and force inputs to determine the gesture, and thus process the gesture input. On the contrary, if the centroid has not moved, the method  200  may proceed to operation  220  and the processor  124  may process the touch inputs. After operations  220 ,  222  and the method  200  may proceed to the end state  224 . 
     CONCLUSION 
     The foregoing description has broad application. For example, while examples disclosed herein may focus on computing devices having touch interfaces, it should be appreciated that the concepts disclosed herein may equally apply to substantially any other type of communication devices. Similarly, although the touch detection is discussed with touch screens, the devices and techniques disclosed herein are equally applicable to other types of capacitive coupling systems. Accordingly, the discussion of any embodiment is meant only to be exemplary and is not intended to suggest that the scope of the disclosure, including the claims, is limited to these examples.