Circular touch sensor

Abstract

A circular touch sensor has three or more sensors arranged in an iris pattern. Each pad is defined by continuous edges that spiral outward about a center point. The unique geometric shape allows measurement of relative amounts of contact on adjoining sensors. In one implementation, the sensors measure relative capacitance of two or more sensors, thereby enabling high precision identification of the point of contact. With as few as three pads, the circular touch sensor is less expensive than traditional 12-pad to 16-pad circular sensors.

1 . A touch sensor, comprising: 
 multiple sensor pads arranged about a center point in an iris pattern, where each sensor pad has at least one associated edge that spirals about the center point to a boundary; and    circuitry coupled to the sensor pads to detect contact to one or more of the sensor pads.    
   
   
       2 . A touch sensor as recited in  claim 1 , wherein the multiple sensor pads comprises not more than four sensor pads.  
   
   
       3 . A touch sensor as recited in  claim 1 , wherein the multiple sensor pads are electrically conductive.  
   
   
       4 . A touch sensor as recited in  claim 1 , wherein: 
 the multiple pads are electrically conductive; and    the circuitry comprises capacitance meters to sense capacitance change in the multiple sensor pads.    
   
   
       5 . A touch sensor as recited in  claim 1 , wherein the circuitry senses pressure applied to one or more of the sensor pads.  
   
   
       6 . A touch sensor as recited in  claim 1 , wherein the circuitry generates values indicative of relative amounts of contact among the sensor pads.  
   
   
       7 . A touch sensor as recited in  claim 1 , wherein the multiple sensor pads are arranged with in multiple, repeating iris patterns set apart by intermediate boundaries, such that within each pattern, each sensor pad has at least one associated edge that spirals about the center point to the intermediate boundary.  
   
   
       8 . A system comprising: 
 the touch sensor as recited in  claim 1;  and    means for determining a location of the contact on the touch sensor.    
   
   
       9 . A system comprising: 
 the touch sensor as recited in  claim 1 , wherein the circuitry generates values representative of the contact to one or more of the sensor pads; and    means for determining a location of the contact on the touch sensor from the values by deriving a ratio indicative of relative contact among the one or more sensor pads, the ratio being used to ascertain the location of the contact on the touch sensor.    
   
   
       10 . An electronics device comprising the touch sensor as recited in  claim 1 .  
   
   
       11 . A pad assembly for a touch sensor, comprising: 
 N sensor pads arranged about a center point; and    each sensor pad defining approximately 1/N of a contact region defined by first and second boundaries, where the second boundary is farther from the center point than the first boundary, and said each sensor pad having at least one associated edge that originates at the first boundary and spirals about the center point through the contact region to the second boundary.    
   
   
       12 . A pad assembly as recited in  claim 11 , wherein the sensor pads consist of three sensor pads (N=3).  
   
   
       13 . A pad assembly as recited in  claim 11 , wherein the sensor pads are made of an electrically conductive material.  
   
   
       14 . A pad assembly as recited in  claim 11 , wherein sensor pads are arranged such that the second boundary forms a circle.  
   
   
       15 . A pad assembly as recited in  claim 11 , wherein the edge originates at a first point on the first boundary and terminates at a second point on the second boundary, wherein the first and second points are at least 120° apart.  
   
   
       16 . A pad assembly as recited in  claim 11 , wherein the edge originates at a first point on the first boundary and terminates at a second point on the second boundary, wherein the first and second points are approximately 180° apart.  
   
   
       17 . A pad assembly as recited in  claim 11 , further comprising a center pad defined within the first boundary.  
   
   
       18 . A sensor system, comprising: 
 the pad assembly as recited in  claim 11;  and    circuitry coupled to the sensor pads to detect contact to one or more of the sensor pads.    
   
   
       19 . A sensor system, comprising: 
 the pad assembly as recited in  claim 11;  and    means for detecting contact to one or more of the sensors and determining a location of the contact.    
   
   
       20 . A device, comprising: 
 a processor; and    a circular touch sensor coupled to provide user input controls to the processor, the circular touch sensor comprising: 
 multiple sensor pads arranged about a center point; and  
 each sensor pad having at least one associated edge that originates at a first boundary and spirals about the center point to a second boundary, where the second boundary is farther from the center point than the first boundary.