Abstract:
A touch screen apparatus and associated methods are disclosed. In one embodiment, a touch screen apparatus includes a touch screen sensor grid including a first electrode and a second electrode. The first electrode includes a cavity in which a ground electrode is disposed. The second electrode is disposed above the ground electrode.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    This disclosure relates to touch screens, and more particularly, to capacitive touch screens. 
         [0003]    2. Description of the Related Art 
         [0004]    Touch screens have found widespread application in recent years. Smart phones and tablet computers are just two of a wide variety of systems in which touch screens are used as input devices. In general, a touch screen is an electronic visual display through which a user can interact with a system by touching the screen with a finger or a stylus. Touch screens come in various types. A category of touch screens that operate based on the changing of capacitance values when touched are referred to as capacitive touch screens. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    A touch screen apparatus is disclosed. In one embodiment, a touch screen apparatus includes a touch screen sensor grid including a first electrode and a second electrode. The first electrode includes a cavity in which a ground electrode is disposed. The second electrode is disposed above the ground electrode. 
         [0006]    In one embodiment, a method includes generating an electric field between a first electrode and a second electrode of a touch screen apparatus. The first electrode includes a cavity in which a ground electrode is disposed. The second electrode disposed above the ground electrode. The method further includes detecting a change of the electric field responsive to a touch of the touch screen apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Other aspects of the disclosure will become apparent upon reading the following detailed description and upon reference to the accompanying drawings, which are now described as follows. 
           [0008]      FIG. 1  is an illustration of one embodiment of an electronic device including a touch screen. 
           [0009]      FIGS. 2A-2D  are illustrations of the various layers of one embodiment of a touch screen apparatus. 
           [0010]      FIG. 3  is a side view illustrating the various layers of one embodiment of a touch screen apparatus. 
           [0011]      FIG. 4  is a schematic diagram illustrating one embodiment of an electrical circuit formed using an embodiment of a touch screen apparatus. 
           [0012]      FIG. 5  is a flow diagram illustrating one embodiment of a method for operating a touch screen apparatus. 
       
    
    
       [0013]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and description thereto are not intended to limit the invention to the particular form disclosed, but, on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0014]    Turning now to  FIG. 1 , an illustration of one embodiment of a portable electronic device including a touch screen apparatus is shown. Portable electronic device  10  in the illustrated example may be one of a number of different types of devices, such as a smart phone, a tablet computer, or other type of device. Touch screen apparatus  25  of portable electronic device  10  provides a user interface in the embodiment shown. The touch screen apparatus  25  may be used as a device in which users provide input to portable electronic device  10 , as well as a device in which responses to user inputs and other processing actions are displayed. Responsive to touch by finger  15  as shown in the illustration, portable electronic device  10  may perform various processing functions that may cause the information displayed to be updated. It is noted that in some embodiments, a stylus or other type of object may be used to provide user input to portable electronic device  10  in lieu of the finger shown in the illustration. In general, the touch may be performed by any suitable object. 
         [0015]    While the embodiment shown in  FIG. 1  is directed to a portable electronic device, touch screen apparatus  25  may be used in other implementations, which may or may not be portable. For example, an embodiment of touch screen apparatus  25  to be discussed further below may be implemented in a kiosk or other type of stationary display or exhibit as well as in other suitable devices. 
         [0016]    In one embodiment, touch screen apparatus  25  may implement a capacitive touch screen. A capacitive touch screen is one in which a touch of the touch screen alters the capacitance between electrodes implemented therein. The change in capacitance may in turn result in a change in an amount of current or charge received by a receiver circuit. Detection of the change of current or charge may indicate that the touch screen has been touched. Touch screen apparatus  25  may include a number of transmit electrodes and receive electrodes arranged across the area spanned by the touch screen. Corresponding electric fields may be formed between transmit and receive electrodes where they overlap in area. Thus, when a particular electric field is disturbed responsive to a touch of the touch screen, circuitry coupled to the touch screen apparatus  25  may detect the location of the touch. Responsive to detecting the touch and its location, the circuitry may perform additional processing that may cause the information displayed on the touch screen to be updated, among other actions. 
         [0017]    In some devices, it may be desirable to limit the thickness of touch screens and the corresponding apparatus embodiments in which they are implemented. In a thinner panel design, the mutual capacitance between the transmit and receive electrodes may be more tightly coupled. Reducing the overlap between the transmit and receive electrodes may help maintain the mutual capacitance at or near a desired value even if the relative geometry therebetween changes as a result of a temperature change. Various embodiments of such a touch screen apparatus will now be discussed in further detail. 
         [0018]    Turning now to  FIGS. 2A-2D , a top view of a portion of various components of touch screen apparatus  25  is shown.  FIG. 2A  illustrates a composite view of the electrode arrangement of touch screen apparatus  25 , while  FIGS. 2B-2D  illustrate the individual electrode types. It is noted that the embodiments shown in  FIGS. 2A-2D  illustrate a portion of the overall area occupied by the different electrodes of touch screen apparatus  25  in various embodiments. It is further noted that the shapes of the various electrodes illustrated here are exemplary, and that such electrodes may be implemented using other shapes while still falling within the scope of this disclosure. 
         [0019]    In the illustrated embodiment, touch screen apparatus  25  includes a number of transmit electrodes  252 , a number of receive electrodes  258 , and a number of ground electrodes  255 . The area occupied by each of transmit electrodes  252  overlaps a portion of the area occupied (in another plane) by each of a number of receive electrodes  258 . Similarly, the area occupied by each of receive electrodes  258  overlaps a portion of the area occupied by each of the transmit electrodes  252 . As will be illustrated in further detail below, each of the transmit electrodes may be coupled to a corresponding driver circuits, while each of receive electrodes  258  may be coupled to a corresponding receiver. When the transmitter and receiver circuits are active, electric fields may be formed between overlapping portions of transmit electrodes  252  and receive electrodes  258 . When touch screen apparatus  25  is touched by a user, at least one of the electric fields may be disturbed due to a change in the capacitance resulting from the touch. The change in the electric field (and more particularly, change in current or charge received by a corresponding receiver) may in turn provide an indication of both the occurrence and location of the touch. 
         [0020]    As noted above, reducing the overlapping area between transmit and receive electrodes may reduce some of the mutual capacitance therebetween and thus reduce the impact of unintended changes to the geometry of the electrodes (e.g., due to temperature changes). In the embodiment shown, cavity areas  253  are slots formed in each of transmit electrodes  252 . The cavity areas  253  are formed in locations that reduce the overlapping area with receive electrodes  258  when touch screen apparatus  25  is fully assembled. 
         [0021]    In the composite assembly shown in  FIG. 2A , the transmit electrodes  252  and receive electrodes  258  are arranged in proximate to one another. The receive electrodes  258  are located in a layer/plane arranged above (i.e., closer to the outer surface of the touch screen apparatus  25 ) the layer/plane in which the transmit electrodes  252  are located. Furthermore, the transmit electrodes  252  are arranged closer to the electronics of the system in which touch screen apparatus  25  is implemented. Since the electronics of the device may generate noise or interference that can affect operation of the touch screen apparatus, ground electrodes  255  are implemented to provide shielding between the device electronics and the receive electrodes  258 . In the embodiment shown, the ground electrodes  255  are shaped such that they may substantially occupy the area between individual instances of the transmit electrodes  252 . Furthermore, the shape of the ground electrodes in this embodiment is such that they also occupy the cavity areas  253  of the transmit electrodes. In one embodiment, the ground electrodes  253  may further be implemented in the same layer/plane as the transmit electrodes  252 . In another embodiment, the layer in which the ground electrodes are implemented may overlap the layer of the transmit electrodes, even if they are otherwise not co-planar. Accordingly, transmit electrodes  252  in combination with ground electrodes  255  may shield receive electrodes  258  from noise generated by the electronics of the device in which touch screen apparatus  25  is implemented. Accordingly, the configuration shown in the illustrated embodiment may allow for reducing the overlap between transmit electrodes  252  and receive electrodes  258  while also providing the shielding from electronic noise as described above. 
         [0022]    Turning now to  FIG. 3 , a side view of one embodiment of a portable electronic device  10  including touch screen apparatus  25  is shown. In the embodiment shown, touch screen apparatus  25  includes a transparent (or at least partially transparent), surface  259 , which may be comprises of an electrically insulating material, and which may additionally be a dielectric material. The surface  259  is arranged as the outermost layer of touch screen apparatus  25 , and may thus act as the touch surface through which a user may provide input to portable electronic device  10 . When a user touches surface  259 , either with a finger or other type of object (e.g., a stylus), the capacitance in the corresponding location may be altered, thereby altering one or more electrical fields in that location. 
         [0023]    In addition, information may be displayed through the transparent, surface  259 . Although not explicitly shown here, portable electronic device may include one or more liquid crystal displays (LCDs), light emitting diode (LED) displays, or other type of display apparatus that may emit light through surface  259 . The displayed information may include icons, text, and any other type of information which may be generated by portable electronic device  10 . A user may interact with portable electronic device  10  by touching the surface  259  at various points. The information displayed by the device may be updated responsive to a user touch. 
         [0024]    In  FIG. 3 , the planar relationships between transmit electrodes  252 , receive electrodes  258  and ground electrodes  255  are shown for one embodiment. In the embodiment shown, receive electrodes are arranged in a layer that is underneath that of surface  259 , while being above (but in the proximity) the plane of transmit electrodes  252 . In turn, the transmit electrodes  252  are arranged in a plane that is above the device/sensor electronics  305  but below the plane of receive electrodes  258 . In the illustrated embodiment, ground electrodes  255  are arranged to have substantially the same planar relationship with receive electrodes  258  as transmit electrodes  252 . Thus, in accordance with both  FIG. 3  and the arrangement shown in  FIGS. 2A-2D , ground electrodes  255  occupy the space between individual instances of transmit electrodes  252 , as well as the cavity areas  253  of each transmit electrode  252 . Therefore, transmit electrodes  252  and ground electrodes  255  may shield receive electrodes  258  from electronic noise that may be emitted by device/sensor electronics  305 . 
         [0025]    In the embodiment shown, each transmit electrode  252  is coupled to a corresponding driver circuit  310 . Similarly, each receive electrode  258  is coupled to a receiver circuit  315 . One instance each of driver circuit  310  and receiver circuit  315  are shown here for the sake of simplicity, although it is understood that multiple instances of each may be provided. Each driver circuit  310  may generate a voltage that is provided to its correspondingly coupled transmit electrode  252 . Each receiver circuit  315  may receive an electrical current or charge from its correspondingly coupled receive electrode  258 . As noted above, when a driver circuit  310  coupled to a transmit electrode  252  and a receiver circuit  315  coupled to an overlapping receiver circuit  315  are both active, an electrical field may be formed in the space between the overlapping electrodes. This electric field may remain substantially constant in strength when undisturbed. When a touch occurs to the surface  259  in a location overlapping the area of the electric field (or close thereto in some cases), the electric field may be altered, and thus the electrical current or charge received by receiver circuit  315  may be correspondingly altered. Thus, a change to the electrical current or charge received by a given receiver circuit  315  may be interpreted as a touch of the touch screen. 
         [0026]    In the embodiment shown, device/sensor electronics  305  may include one or more sensing circuits coupled to one or more of the receiver circuits  315 . Based on which receiver circuits  315  report a change in received current or charge, sensing circuits within device/sensor electronics  305  may determine an approximate location on the surface  259  at which the touch occurred. Based on the touch, an appropriate response may be generated. Exemplary responses include (but are not limited to) updating or changing information, initiating a phone call, answering a phone call, typing a character of a text message, sending a text message, invoking an application, and so on. 
         [0027]    In addition to the sensing circuitry discussed above, device/sensor electronics  305  may include various other types of circuits. Such circuits may include (but are not limited to) general-purpose processors/processor cores, graphics processors, various types of radio transceivers, audio processing circuitry, and so on. The circuitry of device/sensor electronics  305  may be implemented using one or more integrated circuits. In additional, some portions of device/sensor electronics may be implemented using one or more discrete components. 
         [0028]      FIG. 4  is a diagram illustrating the electrical circuit formed overlapping portions of a transmit electrode and a receive electrode and their correspondingly coupled driver and receiver circuits, respectively. In the embodiment shown, touch screen apparatus  25  is represented by a variable capacitance. The capacitance between a transmit electrode  252  and an overlapping portion of a receive electrode may be considered variable due to the change that occurs responsive to a touch in the corresponding proximity. As noted above, driver circuit  310  may generate a voltage that is provided to the transmit electrode  252  of the overlapping portions. Receiver circuit  315  may be coupled to the receive electrode  258  of the overlapping portions. In one embodiment, driver circuit  310  may generate an alternating current (AC) voltage. Accordingly, receiver circuit  315  may receive an AC signal via the formed capacitor. When a touch alters the capacitance of the overlapping sections of the transmit electrode  252  and the receive electrode  258 , the current of the AC signal may change accordingly. This change in current may be detected by receiver circuit  315  and reported to device/sensor electronics  305 , which may then determine the location upon which the touch occurred. 
         [0029]      FIG. 5  is a flow diagram illustrating one embodiment of a method for operating a touch screen apparatus. The methodology described herein and illustrated by  FIG. 5  may be applied to the various embodiments of touch screen apparatus  25  discussed above, among others. 
         [0030]    Method  500  begins with the generation of electric fields between transmit electrodes and receive electrodes of a touch screen apparatus (block  505 ). The electric fields may be generated based on a capacitance between overlapping portions of transmit and receive electrodes of a touch screen apparatus. The electrodes may be arranged such that ground electrodes fill in gaps between and in the transmit electrodes t shield the receive electrodes from electronic noise generated by other circuits in the system in which the touch screen apparatus is implemented. 
         [0031]    The method further includes detecting a change in at least one of the electric fields responsive to a touch of the touch screen (block  510 ). The change in the electric field may result from a change in capacitance between transmit and receive electrodes in the proximity of the touch. The change in the electric field may be detected via a change in current received by a receiver circuit coupled to a corresponding receive electrode. The detection of the changing current may be reported to sensor electronics in one embodiment, which may in turn determine the location of the touch (block  515 ). The system in which the touch screen apparatus is implemented may generate a system response to the touch upon its detection and determination of its location (block  520 ). The responsive may include one of a number of different actions, some of which may include an update of the information displayed on the touch screen. The method may return to block  510  and repeat blocks  510 ,  515 , and  520  for each touch of the touch screen. 
         [0032]    While the present invention has been described with reference to particular embodiments, it will be understood that the embodiments are illustrative and that the invention scope is not so limited. Any variations, modifications, additions, and improvements to the embodiments described are possible. These variations, modifications, additions, and improvements may fall within the scope of the inventions as detailed within the following claims.