PATENT DOCUMENT

Publication Number: US-9069404-B2
Application Number: US-47125109-A
Country: US
Kind Code: B2

Title: Force imaging input device and system

Abstract:
A force imaging touch pad includes first and second sets of conductive traces separated by a spring membrane. When a force is applied, the spring membrane deforms moving the two sets of traces closer together. The resulting change in mutual capacitance is used to generate an image indicative of the amount or intensity of the applied force. A combined location and force imaging touch pad includes two sets of drive traces, one set of sense traces and a spring membrane. In operation, one of the drive traces is used in combination with the set of sense traces to generate an image of where one or more objects touch the touch pad. The second set of drive traces is used in combination with the sense traces and spring membrane to generate an image of the applied force&#39;s strength or intensity.

Claims:
What is claimed: 
     
       1. A location and force imaging system comprising:
 a first member that receives a force input on a first surface and that includes a first conductive element configured for receiving first drive signals for detecting a location of the force input; and 
 a second member including a second conductive element configured for receiving second drive signals for detecting an intensity of the force input, the second member spatially separated from the first member through a mechanism by which the first and second members are brought into closer proximity when the force input is received by the first surface; 
 wherein the first and second conductive elements are configured for generating information associated with an image of the intensity of the force input and an image of the location of the force input. 
 
     
     
       2. The system of  claim 1 , wherein the first conductive element includes a first plurality of conductive traces. 
     
     
       3. The system of  claim 2 , wherein the second conductive element includes a second plurality of conductive traces. 
     
     
       4. The system of  claim 1 , further comprising a deformable member disposed between the first member and the second member, wherein the deformable member provides the mechanism by which the first and second members are brought into closer proximity when the force input is received by the first surface. 
     
     
       5. The system of  claim 4  wherein the deformable member includes a dielectric membrane. 
     
     
       6. The system of  claim 1 , further comprising a plurality of sense traces for sensing the location of the force input and the intensity of the force input. 
     
     
       7. The system of  claim 1 , further comprising a base layer adjacent to the second member. 
     
     
       8. The system of  claim 1 , the mechanism comprising a deformable dielectric membrane disposed at least partially between and contacting at least a portion of the first and second members. 
     
     
       9. The system of  claim 1 , further comprising a controller configured for receiving the information and computing the images of the intensity and location of the force input, and transmitting signals representing the images of the intensity and location of the force input. 
     
     
       10. The system of  claim 9 , further comprising a host processor that receives the signals and performs command and control actions based on the images of the intensity and location of the force input. 
     
     
       11. The system of  claim 10 , wherein the command and control actions include selecting an object displayed on a display unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/278,080, entitled “Force Imaging Input Device and System,” filed Mar. 30, 2006, the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The invention relates generally to electronic system input devices and, more particularly, to force imaging and location-and-force imaging mutual capacitance systems. 
     Numerous touch sensing devices are available for use in computer systems, personal digital assistants, mobile phones, game systems, music systems and the like (i.e., electronic systems). Perhaps the best known are resistive-membrane position sensors which have been used as keyboards and position indicators for a number of years. Other types of touch sensing devices include resistive tablets, surface acoustic wave devices, touch sensors based on resistance, capacitance, strain gages electromagnetic sensors or pressure sensors, and optical sensors. Pressure sensitive position sensors have historically offered little benefit for use as a pointing device (as opposed to a data entry or writing device) because the pressure needed to make them operate inherently creates stiction between the finger and the sensor surface. Such stiction has, in large measure, prevented such devices from becoming popular. 
     Owing to the growth popularity of portable devices and the attendant need to integrate all input functions into a single form factor, the touch pad is now one of the most popular and widely used types of input device. Operationally, touch pads may be categorized as either “resistive” or “capacitive.” In resistive touch pads, the pad is coated with a thin metallic electrically conductive layer and resistive layer. When the pad is touched, the conductive layers come into contact through the resistive layer causing a change in resistance (typically measured as a change in current) that is used to identify where on the pad the touch event occurred. In capacitive touch pads, a first set of conductive traces run in a first direction and are insulated by a dielectric insulator from a second set of conductive traces running in a second direction (generally orthogonal to the first direction). The grid formed by the overlapping conductive traces create an array of capacitors that can store electrical charge. When an object is brought into proximity or contact with the touch pad, the capacitance of the capacitors at that location change. This change can be used to identify the location of the touch event. 
     One drawback to using touch pads as input devices is that they do not generally provide pressure or force information. Force information may be used to obtain a more robust indication of how a user is manipulating a device. That is, force information may be used as another input dimension for purposes of providing command and control signals to an associated electronic device. Thus, it would be beneficial to provide a force measurement system as part of a touch pad input device. 
     SUMMARY 
     In one embodiment the invention provides a force sensitive touch pad that includes first and second sets of conductive traces separated by a spring membrane. When a force is applied, the spring membrane deforms moving the two sets of traces closer together. The resulting change in mutual capacitance is used to generate an image indicative of the location (relative to the surface of the touch pad) and strength or intensity of an applied force. In another embodiment, the invention provides a combined location and force sensitive touch pad that includes two sets of drive traces, one set of sense traces and a spring membrane. In operation, one of the drive traces is used in combination with the set of sense traces to generate an image of where one or more objects touch the touch pad. The second set of drive traces is used in combination with the sense traces and spring membrane to generate an image of the applied force&#39;s strength or intensity and its location relative to the touch pad&#39;s surface. Force touch pads and location and force touch pads in accordance with the invention may be incorporated in a variety of electronic devices to facilitate recognition of an increased array of user manipulation. 
     In yet another embodiment, the described force sensing architectures may be used to implement a display capable of detecting the amount of force a user applies to a display (e.g., a liquid crystal display unit). Display units in accordance with this embodiment of the invention may be used to facilitate recognition of an increased array of user input. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows, in exploded perspective view, a force detector in accordance with one embodiment of the invention. 
         FIGS. 2A and 2B  show, in cross-section, an unloaded (A) and loaded (B) force detector in accordance with  FIG. 1 . 
         FIG. 3  shows, in block diagram form, a force detection system in accordance with one embodiment of the invention. 
         FIG. 4  shows, in block diagram form, a more detailed view of the force detection system in accordance with  FIG. 3 . 
         FIG. 5  shows, in cross-section, a location and force detection device in accordance with one embodiment of the invention. 
         FIG. 6  shows, in cross section, a location and force detection device in accordance with another embodiment of the invention. 
         FIG. 7  shows an exploded view of drive and sense traces in accordance with  FIG. 6 . 
         FIGS. 8A-8C  show various views of a location and force detection device in accordance with still another embodiment of the invention. 
         FIGS. 9A-9C  show various views of a location and force detection device in accordance with yet another embodiment of the invention. 
         FIGS. 10A and 10B  show, in cross section, a location and force detection device in accordance with another embodiment of the invention. 
         FIGS. 11A-11C  show various views of a spring membrane in accordance with another embodiment of the invention. 
         FIGS. 12A and 12B  show, in block diagram form, a force detection display system in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the invention as claimed and is provided in the context of the particular examples discussed below (touch pad input devices for personal computer systems), variations of which will be readily apparent to those skilled in the art. Accordingly, the claims appended hereto are not intended to be limited by the disclosed embodiments, but are to be accorded their widest scope consistent with the principles and features disclosed herein. By way of example only, force imaging systems in accordance with the invention are equally applicable to electronic devices other than personal computer systems such as computer workstations, mobile phones, hand-held digital assistants and digital control panels for various machinery and systems (mechanical, electrical and electronic). 
     Referring to  FIG. 1 , the general concept of a force detector in accordance with the invention is illustrated as it may be embodied in touch pad device  100 . As illustrated, force detector  100  comprises cosmetic layer  105 , sense layer  110  (including conductive paths  115  and electrical connector  120 ), dielectric spring layer  125  (including spatially offset raised structures  130 ), drive layer  135  (including conductive paths  140  and electrical connector  145 ) and base or support  150 . (It will be understood by those of ordinary skill in the art that connectors  120  and  145  provide unique connections for each conductive trace on layers  110  and  135  respectively.) 
     Cosmetic layer  105  acts to protect other elements of the system from ambient conditions (e.g., dust and moisture) and, further, provides a surface through which users interact with detector  100 . Conductive paths  115  on sense layer  110  are arranged so that they overlap conductive paths  140  on drive layer  135 , thereby forming capacitors whose plates (conductive paths  115  and  140 ) are separated by sense layer substrate  110 , dielectric spring layer  125  and raised structures  130 . Dielectric spring layer  125  and raised structures  130  together create a mechanism by which sense layer  110 &#39;s conductive paths  115  are brought into closer proximity to drive layer  135 &#39;s conductive paths  140  when a force is applied to cosmetic layer  105 . It will be recognized that this change in separation causes the mutual capacitance between sense layer and drive layer conductive paths ( 115  and  140 ) to change (increase)—a change indicative of the amount, intensity or strength of the force applied to cosmetic layer  105 . Base or support layer  150  provides structural integrity for force detector  100 . 
     Referring to  FIG. 2A , a cross-sectional view of force detector  100  is shown in its unloaded or “no force” state. In this state, the mutual capacitance between sense layer  110  and drive layer  135  conductive paths ( 115  and  140 ) results in a steady-state or quiescent capacitance signal (as measured via connectors  120  and  145  in  FIG. 1 ). Referring to  FIG. 2B , when external force  200  is applied to cosmetic layer  105 , dielectric spring layer  125  is deformed so that sense layer  110  moves closer to drive layer  135 . This, in turn, results in a change (increase) in the mutual capacitance between the sense and drive layers—a change that is approximately monotonically related to the distance between the two and, therefore, to the intensity or strength of applied force  200 . More specifically, during operation traces  140  (on drive layer  135 ) are electrically stimulated one at a time and the mutual capacitance associated with the stimulated trace and each of traces  115  (on sense layer  110 ) is measured. In this way an image of the strength or intensity of force  200  applied to cosmetic layer  105  is obtained. As previously noted, this change in mutual capacitance may be determined though appropriate circuitry. 
     Referring to  FIG. 3 , a block diagram of force imaging system  300  utilizing force detector touch pad  100  is shown. As illustrated, force imaging system  300  comprises force detector  100  coupled to touch pad controller  305  through connectors  120  (for sense signals  310 ) and  145  (for drive signals  315 ). Touch pad controller  305 , in turn, periodically sends signals to host processor  320  that represent the (spatial) distribution of force applied to detector  100 . Host processor  320  may interpret the force information to perform specified command and control actions (e.g., select an object displayed on display unit  325 ). 
     Referring to  FIG. 4 , during operation drive circuit  400  in touch pad controller  305  sends (“drives”) a current through drive signals  315  and connector  145  to each of the plurality of drive layer conductive paths  140  (see  FIG. 1 ) in turn. Because of capacitive coupling, some of this current is carried through to each of the plurality of sense layer conductive paths  115  (see  FIG. 1 ). Sensing circuits  405  (e.g., charge amplifiers) detect the analog signal from sense signals  310  (via connector  120 ) and send them to analysis circuit  410 . One function of analysis circuit  410  is to convert the detected analog capacitance values to digital form (e.g., through A-to-D converters). Another function of analysis circuit is to queue up a plurality of digitized capacitance values for transmission to host processor  320  (see  FIG. 3 ). Yet another function of analysis circuit is to control drive circuit  400  and, perhaps, to dynamically adjust operation of sense circuits  405  (e.g., such as by changing the threshold value at which a “change” in capacitance is detected). One embodiment of controller  305  suitable for use in the present invention is described in U.S. patent application entitled “Multipoint Touch Screen Controller,” Ser. No. 10/999,999 by Steve Hotelling, Christoph Krah and Brian Huppi, filed 15 Mar. 2006 and which is hereby incorporated in its entirety. 
     In another embodiment, a force detector in accordance with the invention is combined with a capacitive location detector to create a touch pad device that provides both location and force detection. Referring to  FIG. 5 , combined location and force detector  500  comprises cosmetic layer  505 , circuit board or substrate  510  (including a first plurality of conductive drive paths  515  on a first surface and a plurality of sense paths  520  on a second surface), dielectric spring layer  525  (including alternating, or spatially offset, raised structures  530 ), drive layer  535  (including a second plurality of conductive drive paths) and base or support  540 . In one embodiment, conductive drive paths  515  and  535  are laid down on substrate  510  and support  540  respectively to form rows and sense conductive paths are laid down on substrate  510  to form columns. Accordingly, during operation first drive paths  515  are driven (one at a time) during a first time period and, during this same time, sense paths  520  are interrogated to obtain an image representing the location of one or more cosmetic layer touches. Similarly, second drive paths  535  are driven (one at a time) during a second time period and, during this same time, sense paths  520  are again interrogated to obtain an image representing, this time, the strength or intensity of the force applied to cosmetic layer  505 . The operation of computer input devices (e.g., touch pads) for touch detection based on the principle of mutual capacitance is described in U.S. patent application entitled “Multipoint Touchscreen” by Steve Hotelling, Joshua A. Strickon and Brian Q. Huppi, Ser. No. 10/840,862 and which is hereby incorporated in its entirety. 
     Referring to  FIG. 6 , location and force touch pad  600  in accordance with another embodiment of the invention is shown in cross section. In this embodiment, cosmetic layer  605  comprises a polyester or polycarbonate film. Layer  610  comprises an acrylic-based pressure sensitive or ultraviolet light cured adhesive. Layer  615  functions as a two-sided circuit board that has a first plurality of conductive drive traces  620  oriented in a first direction on a “top” surface (i.e., toward cosmetic layer  605 ) and a plurality of conductive sense traces  625  oriented in a second direction on a “bottom” surface. In one embodiment, circuit substrate layer  615  comprises a low temperature plastic or thermoplastic resin such as polyethylene terephthalate (“PET”. In this embodiment, drive traces  620  and sense traces  625  may comprise printed silver ink. In another embodiment, circuit substrate layer  615  comprises a flexible circuit board, or fiberglass or glass and drive and sense traces ( 620  and  625 ) comprise Indium tin oxide (“ITO”) or copper. Layer  630 , in one embodiment, comprises a layered combination consisting of adhesive-PET-adhesive, where the adhesive components are as described above with respect to layer  610 . Layers  635 ,  640  and  645  comprise PET of varying thicknesses. As shown, the “bottom” surface of layer  640  has affixed thereon a second plurality of conductive drive traces  650  oriented in substantially the same orientation as first conductive drive traces  620 . Raised and spatially offset support structures  655  and layer  660  also comprise a layered combination consisting of adhesive-PET-adhesive (similar to layer  630 , see above). Layers  605 - 660  are affixed to and supported by base or stiffener plate  665 . For example, in a portable or notebook computer system, base  665  could be formed from a rigid material such as a metal stamping that is part of the computer system&#39;s frame. Similarly, base  665  could be the internal framing within a personal digital assist and or mobile telephone. Table 1 identifies the thickness for each of layers  600 - 660  for one embodiment of touch pad  600 . 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Dimensions for Illustrative Touch Pad 600 
               
            
           
           
               
               
               
            
               
                 Layer 
                 Material 
                 Thickness (mm) 
               
               
                   
               
               
                 605 
                 Polyester, polycarbonate film, glass or ceramic 
                 0.3  
               
               
                 610 
                 Pressure sensitive adhesive (“PSA”) or 
                 0.05  
               
               
                   
                 ultraviolet (“UV”) light cured adhesive 
               
               
                 615 
                 PET 
                 0.075 ± 0.02 
               
               
                 620 
                 Silver ink, copper, Indium tin oxide 
                 0.006 
               
               
                 625 
                 Silver ink, copper, Indium tin oxide 
                 0.006 
               
               
                 630 
                 Layered PSA-PET-PET 
                  0.03 ± 0.01 
               
               
                 635 
                 PET 
                 0.075 ± 0.02 
               
               
                 640 
                 PET 
                  0.1 ± 0.02 
               
               
                 645 
                 PET 
                 0.125 ± 0.02 
               
               
                 650 
                 Silver ink, copper, Indium tin oxide 
                 0.006 
               
               
                 655 
                 Layered: PSA 
                 0.025 ± 0.01 
               
               
                   
                 PET 
                  0.1 ± 0.02 
               
               
                   
                 PSA 
                 0.025 ± 0.01 
               
               
                   
               
               
                 Active touch pad surface: 271 mm × 69 mm 
               
               
                 No of drive traces (620 and 650): 13 
               
               
                 Number of sense traces (625): 54 
               
               
                 Pixel seperation: 5 mm 
               
            
           
         
       
     
     In operation touch pad  600  measures the change (e.g., decrease) in capacitance due to cosmetic layer  605  being touched at one or more locations through the mutual capacitance between drive traces  620  and sense traces  625 . In a manner as described above, touch pad  600  also measures forces applied to cosmetic layer as sense traces  625  and drive traces  650  are brought into closer proximity through the measured change (e.g., increase) in mutual capacitance between them. In this embodiment, raised structures  655  are used on both sides of the second layer of drive traces ( 650 ) to provide additional movement detection capability. 
     During measurement operations, each of drive traces  620  are stimulated in turn and, simultaneously, the change in mutual capacitance between drive traces  620  and sense traces  625  is measured. Once each of drive traces  620  have been stimulated (and the corresponding change in capacitance measured via sense traces  625 ), each of drive traces  650  are driven in turn and sense traces  625  are used to determine the change in mutual capacitance related to force (that is, the mutual capacitance change between traces  625  and  650  due to an applied force). In this manner, images of both the “touch” input and “force” input to cosmetic layer  605  can be obtained. 
     One of ordinary skill in the art will recognize that the above-described “scanning” sequence is not required. For example, drive traces  620  and  650  could be stimulated in overlapping fashion such that a first trace in drive traces  620  is stimulated, followed by a first trace in drive traces  650 , followed by a second trace in drive traces  620  and so on. Alternatively, groups of traces in drive traces  620  could be stimulated first, followed by a group of traces in drive traces  650 , and so on. 
     In one embodiment drive traces  620  (associated with touch location measurement operations) use a different geometry from drive traces  650  (associated with force measurement operations) and sense traces  625  (used during both location and force measurement operations). Referring to  FIG. 7 , it can be seen that drive traces  620  utilize conductive traces that employ internal floating plate structures  700  and, in addition, are physically larger than either the conductive traces used in sense  625  and drive traces  650  (both of which, in the illustrated embodiment, have the same physical size/structure). It has been found that this configuration provides increased sensitivity for determining where one or more objects (e.g., a finger of stylus) touch, or come into close proximity to, cosmetic surface  605 . 
     Referring to  FIG. 8A , in another embodiment of a combined touch and force sensitive touch pad in accordance with the invention (touch pad  800 ), raised structures  655  may be replaced by beads or polymer dots  805  (also referred to as rubber or elastomer dots). In this embodiment, beads  805  operate in a manner similar to that of raised structures  655  (see  FIG. 6 ). As shown, beads  805  rest on a thin adhesive layer  810  and are sized to keep layers  630  and  640  at a specified distance when no applied force is present. One illustrative layout and spacing of beads  805  is shown in  FIGS. 8B  (lop view) and  8 C (cross-section). Table 2 identifies the approximate dimensions for each component of touch pad  800  that is different from prior illustrated touch pad  600 . 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Dimensions for Illustrative Touch Pad 800 
               
            
           
           
               
               
               
            
               
                 Layer 
                 Material 
                 Thickness (mm) 
               
               
                   
               
               
                 805 
                 Rubber or polymer (e.g., elastomer) 
                   
               
               
                 810 
                 Pressure sensitive adhesive (“PSA”) or 
                  0.015 
               
               
                   
                 ultraviolet (“UV”) light cured adhesive 
               
               
                 a 
                 Column bead separation 
                 1.0 
               
               
                 b 
                 Row bead separation 
                 5.0 
               
               
                 c 
                 Bead offset 
                 2.5 ± 0.15 
               
               
                 d 
                 Bead height 
                  0.15 
               
               
                   
               
               
                 Active touch pad surface: 271 mm × 69 mm 
               
               
                 No of drive traces (620 and 650): 13 
               
               
                 Number of sense traces (625): 54 
               
               
                 Pixel separation: 5 mm 
               
            
           
         
       
     
     Referring to  FIG. 9A , in yet another embodiment of a combined touch and force sensitive touch pad in accordance with the invention (touch pad  900 ), a single layer of deformable beads or elastomer dots  905  are used. In touch pad  900 , thin adhesive layers  910  are used to mechanically couple the beads to the rest of the touch pad structure and the structure itself to base  665 . One illustrative layout and spacing of deformable beads  905  is shown in  FIGS. 9B  (lop view) and  9 C (cross-section). Table 3 identifies the approximate dimensions for each component of touch pad  900  that is different from prior illustrated touch pad  600 . 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Dimensions for Illustrative Touch Pad 900 
               
            
           
           
               
               
               
            
               
                 Layer 
                 Material 
                 Thickness (mm) 
               
               
                   
               
            
           
           
               
               
               
            
               
                 905 
                 Rubber or polymer (e.g., elastomer) 
                   
               
               
                 910 
                 Pressure sensitive adhesive (“PSA”) or 
                 0.015 
               
               
                   
                 ultraviolet (“UV”) light cured adhesive 
               
               
                 a 
                 Column bead separation 
                 1.0 
               
               
                 b 
                 Row bead separation 
                 1.0 
               
               
                 c 
                 Bead offset 
                 0.5 
               
               
                 d 
                 Bead width 
                 0.5 
               
               
                 e 
                 Bead height 
                 0.15 
               
               
                   
               
               
                 Active touch pad surface: 271 mm × 69 mm 
               
               
                 No of drive traces (620 and 650): 13 
               
               
                 Number of sense traces (625): 54 
               
               
                 Pixel separation: 5 mm 
               
            
           
         
       
     
     Referring to  FIG. 10A , in another embodiment of a combined touch and force sensitive touch pad in accordance with the invention (touch pad  1000 ), spring membrane  1005  is used instead of raised structures (e.g.  530  and  655 ) or deformable beads (e.g.,  805  and  905 ). In touch pad  1000 , thin adhesive layers  1010  are used to mechanically couple PET spring  1005  to layers  635  and  640  as well as to mechanically couple layer  645  to base  665 . Referring to  FIG. 10B , in one embodiment spring membrane comprises a single rippled sheet of PET whose run-to-rise ratio (i.e., a/b) is typically in the range of approximately 10:1 to 50:1. One of ordinary skill in the art will recognize that the exact value used in any given embodiment may change due to a variety of factors such as, for example, the physical size of the touch pad surface, the amount of weight specified for full deflection (e.g., 200 grams) and the desired sense of “stiffness” presented to the user. Table 4 identifies the approximate dimensions for each component of touch pad  1000  that is different from prior illustrated touch pad  600 . 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Dimensions for Illustrative Touch Pad 1000 
               
            
           
           
               
               
               
            
               
                 Layer 
                 Material 
                 Thickness (mm) 
               
               
                   
               
               
                 1005 
                 PET 
                 0.75  
               
               
                 1010 
                 Pressure sensitive adhesive (“PSA”) or 
                 0.025 
               
               
                   
                 ultraviolet (“UV”) light cured adhesive 
               
               
                 a/b 
                 Spring run-to-rise ratio 
                 10:1 → 50:1 
               
               
                   
               
               
                 Active touch pad surface: 271 mm × 69 mm 
               
               
                 No of drive traces (620 and 650): 13 
               
               
                 Number of sense traces (625): 54 
               
               
                 Pixel separation: 5 mm 
               
            
           
         
       
     
     Referring to  FIG. 11A , in another embodiment rippled spring membrane  1005  may be replaced by dimpled spring membrane  1105 . In this implementation, spring membrane  1105  is a single sheet of deformable material (e.g., PET) that has dimples formed in it by, for example, thermal or vacuum forming techniques.  FIGS. 11B and 11C  show top views of two possible dimple arrangements. Two illustrative layouts (lop view) for dimpled membrane  1105  are shown in  FIGS. 11B and 11C . As used in  FIGS. 11A-11C , the “+” symbol represents a raised region and a “−” symbol represents a depressed region. Table 5 identifies the approximate dimensions “a” through “e” specified in  FIG. 11A . 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Dimensions for Illustrative Spring Membrane 1100 
               
            
           
           
               
               
               
               
            
               
                   
                 Layer 
                 Material 
                 Thickness (mm) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 1105 
                 PET 
                 0.075 
               
               
                   
                 a 
                 Dimple top length 
                 1.0 
               
               
                   
                 b 
                 Dimple width 
                 1.25 
               
               
                   
                 c 
                 Dimple separation 
                 2.5 
               
               
                   
                 d 
                 Dimple rise and fall length 
                 0.075 
               
               
                   
                   
               
            
           
         
       
     
     Various changes in the materials, components and circuit elements are possible without departing from the scope of the following claims. For example, drive traces and sense traces in accordance with  FIGS. 1-10  have been described as being orthogonal. The manner in which drive traces and cut across or intersect with sense traces, however, generally depends on the coordinate system used. In a Cartesian coordinate system, for example, sense traces are orthogonal to the driving traces thereby forming nodes with distinct x and y coordinates. Alternatively, in a polar coordinate system, sense traces may be concentric circles while drive traces may be radially extending lines (or vice versa). 
     In addition, in the embodiments of  FIGS. 1 and 2 , drive layer  135  and drive traces  140  (and, therefore, connector  145 ) may be incorporated within and on spring membrane  125 . That is, drive traces  140  could be laid down or etched on a surface of flexible membrane  125 . Similarly, drive traces  535  could be incorporated into and as part of flexible membrane  525  (see  FIG. 5 ). 
     One of ordinary skill in the art will also recognize that beads in accordance with  FIGS. 8 and 9  (see  FIGS. 8 and 9 ) could also be used in place of raised structures  130 ,  530  and  655  (see  FIGS. 1 ,  2 A,  2 B,  5  and  6 ). Similarly, spring mechanisms  1005  (see  FIG. 10) and 1105  (see  FIG. 11 ) could be used in place of beads  805  (see  FIG. 8 ), deformable beads  805  and  905  (see  FIGS. 8 and 9 ) or raised structures  130 ,  530  and  655  (see  FIGS. 1 ,  5  and  6 ). 
     Referring to  FIG. 12A , in another embodiment force detection in accordance with the invention may be incorporated within a display unit rather than a touchpad. For example, system  1200  includes processor  1205 , standard input-output (“I/O”) devices  1210  (e.g., keyboard, mouse, touch pad, joy stick and voice input) and display  1215  incorporating force detection capability in accordance with the invention. Referring to  FIG. 12B , in this embodiment, display  1215  includes display element  1220 , display element electronics  1225 , force element  1230  and force electronics  1235 . In this manner, user  1240  views display element  1220  of display  1200  through force element  1230 . By way of example, display element  1220  and electronics  125  may comprise a conventional liquid crystal display (“LCD”) display. Force element  1230  may comprise a force-only sensor (e.g., similar to the embodiments of  FIGS. 1 and 2 ) or a force and location sensor (e.g., similar to the embodiments of  FIGS. 5-11 ). Force electronics  1235  may comprise processing circuitry as described in  FIG. 4 . That is, force electronics  1235  is capable of driving and sensing mutual capacitance signals as described in connection with a touch pad in accordance with the invention. 
     It will be recognized by those of ordinary skill in the art that use of the described force detection technology should, when applied to display  1215 , utilize transparent or substantially transparent drive and sense traces such as that provided by ITO (i.e., rather than copper which is opaque). Similarly, the gap between the first layer of traces (e.g., drive traces) and a second layer of traces (e.g., sense traces) used to detect an applied force (see discussion above) should be transparent or substantially transparent. For example, compressible transparent spacers could be used to embody offset raised structures  130 , support structures  655 , deformable beads  805 ,  905  or spring membranes  1005 ,  1105 .

Metadata:
Filing Date: 20090522
Publication Date: 20150630
Grant Date: 20150630
Priority Date: 20060330
Inventors: HOTELLING STEVEN P.
HUPPI BRIAN Q.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/04166", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0414", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0447", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04106", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0447", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04112", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 38180645