Force Sensing Architectures

Abstract

An electronic device with a force sensing device is disclosed. The electronic device comprises a user input surface defining an exterior surface of the electronic device, a first capacitive sensing element, and a second capacitive sensing element capacitively coupled to the first capacitive sensing element. The electronic device also comprises a first spacing layer between the first and second capacitive sensing elements, and a second spacing layer between the first and second capacitive sensing elements. The first and second spacing layers have different compositions. The electronic device also comprises sensing circuitry coupled to the first and second capacitive sensing elements configured to determine an amount of applied force on the user input surface. The first spacing layer is configured to collapse if the applied force is below a force threshold, and the second spacing layer is configured to collapse if the applied force is above the force threshold.

What is claimed is: 
     
         1 . An electronic device, comprising:
 a user input surface defining an exterior surface of the electronic device;   a first capacitive sensor comprising a first pair of sensing elements having an air gap therebetween and configured to determine a first amount of applied force on the user input surface that results in a collapse of the air gap; and   a second capacitive sensor below the first capacitive sensor comprising a second pair of sensing elements having a deformable element therebetween and configured to determine a second amount of applied force on the user input surface that results in a deformation of the deformable element.   
     
     
         2 . The electronic device of  claim 1 , wherein:
 the first pair of sensing elements comprises:
 a shared sense element; and 
 a first drive element set apart from and capacitively coupled to the shared sense element; and 
   the second pair of sensing elements comprises:
 the shared sense element; and 
 a second drive element set apart from and capacitively coupled to the shared sense element. 
   
     
     
         3 . The electronic device of  claim 2 , further comprising:
 a display layer comprising:
 a display element positioned below the user input surface; and 
 a back polarizer positioned below the display element; 
   a sheet of conductive material formed over a back surface of the back polarizer to produce a conducting surface on the back surface of the back polarizer; and   a conductive border formed along at least one edge of the sheet of conductive material.   
     
     
         4 . The electronic device of  claim 3 , wherein the conductive border is positioned outside of a user-viewable region of the display layer. 
     
     
         5 . The electronic device of  claim 3 , wherein the sheet of conductive material comprises silver nanowire. 
     
     
         6 . The electronic device of  claim 2 , further comprising:
 a display element coupled to the first drive element; and   a base structure, wherein:
 the display element is configured to flex relative to the base structure; 
 the deformable element is coupled to the base structure; and 
 the air gap is positioned between the deformable element and the display element. 
   
     
     
         7 . The electronic device of  claim 6 , wherein the shared sense element is coupled to the deformable element. 
     
     
         8 . A capacitive force sensor for an electronic device, comprising:
 a first drive layer;   a second drive layer positioned relative to the first drive layer;   a shared sense layer between the first and second drive layers;   a first spacing layer between the first drive layer and the shared sense layer; and   a second spacing layer between the shared sense layer and the second drive layer.   
     
     
         9 . The capacitive force sensor of  claim 8 , wherein:
 the first spacing layer comprises an air gap; and   the capacitive force sensor further comprises:
 a pair of opposed surfaces defining the air gap; and 
 an anti-adhesion layer configured to prevent adhesion between the opposed surfaces. 
   
     
     
         10 . The capacitive force sensor of  claim 9 , wherein the second spacing layer comprises an array of deformable protrusions extending from a base layer. 
     
     
         11 . The capacitive force sensor of  claim 8 , further comprising sensing circuitry operatively coupled to the first drive layer, the second drive layer, and the shared sense layer, and configured to determine:
 a first amount of applied force resulting in a change in thickness of the first spacing layer; and   a second amount of applied force resulting in a change in thickness of the second spacing layer.   
     
     
         12 . The capacitive force sensor of  claim 6 , wherein the first drive layer comprises:
 an insulating substrate;   a sheet of conductive material formed over a back surface of the insulating substrate to produce a conducting surface on the back surface of the insulating substrate; and   a conductive border formed along at least one edge of the sheet of conductive material.   
     
     
         13 . The capacitive force sensor of  claim 12 , wherein the conductive border comprises a continuous conductive border that extends along the edges of the sheet of conductive material. 
     
     
         14 . The capacitive force sensor of  claim 12 , wherein the conductive border comprises one or more conductive strips formed along a respective edge of the sheet of conductive material. 
     
     
         15 . An electronic device, comprising:
 a cover defining a user input surface of the electronic device;   a first sensing element coupled to the cover within an interior volume of the electronic device;   a frame member coupled to the cover and extending into the interior volume of the electronic device;   a second sensing element coupled to the frame member; and   a third sensing element coupled to a base structure and set apart from the sense layer.   
     
     
         16 . The electronic device of  claim 15 , wherein:
 the frame member defines an opening; and   the third sensing element capacitively couples with the second sensing element through the opening.   
     
     
         17 . The electronic device of  claim 15 , wherein the first sensing element comprises a continuous layer of transparent conductive material covering substantially an entire surface of a substrate. 
     
     
         18 . The electronic device of  claim 17 , wherein:
 the second sensing element comprises a plurality of sensing regions; and   the continuous layer of transparent conductive material overlaps multiple sensing regions of the plurality of sensing regions.   
     
     
         19 . The electronic device of  claim 18 , wherein:
 the third sensing element comprises a plurality of drive regions; and   each drive region overlaps multiple sensing regions of the plurality of sensing regions.   
     
     
         20 . The electronic device of  claim 17 , wherein:
 the first sensing element further comprises a connection element electrically coupled to the continuous layer of transparent conductive material; and   the electronic device further comprises:
 sensing circuitry configured to provide an electrical signal to the first sensing element; and 
 a connector segment electrically coupling the sensing circuitry to the connection element.