Device and method for solid state capacitive scrolling

Abstract

A capacitive sensing device and method include a touch surface, a capacitive touch sensor coupled to the touch surface and configured to measure finger motion along the touch surface, and a processor in operative communication with the capacitive touch sensor. The processor is configured to generate a scrolling command in response to finger motion along the touch surface, cease the scrolling command without substantially continuing generating the scrolling command upon the finger lifting from the touch surface when the finger is stationary prior to lifting from the touch surface, and continue generating the scrolling command for a time after the finger lifting from the touch surface to emulate coasting responsive to finger motion prior the finger lifting.

1 . A touch sensor system, comprising:
 a touch sensor configured to sense an object along an axis; and   a processor in operative communication with the touch sensor, the processor configured to generate a scrolling signal responsive to sensing motion of the object along the axis, the processor further configured to cease the scrolling signal, without substantially continuing the scrolling signal, responsive to the object being substantially stationary prior to the object lifting from the touch sensor, wherein the processor is further configured to continue the scrolling signal after lifting off of the object from the touch sensor responsive to sensing object motion immediately prior to the object lifting off the touch sensor.   
     
     
         2 . The touch sensor system of  claim 1 , wherein the scrolling signal is compatible with that from a scroll wheel mouse. 
     
     
         3 . The touch sensor system of  claim 1 , wherein the processor is configured to measure the velocity of the object immediately prior to the lifting off from the touch sensor, and wherein the touch sensor is configured to continue the scrolling signal when the velocity exceeds a predetermined threshold. 
     
     
         4 . The touch sensor system of  claim 3 , wherein the predetermined threshold is non-zero. 
     
     
         5 . The touch sensor system of  claim 4 , wherein the scrolling signal includes an indication of a presence of the finger touching the touch surface and a non-zero velocity of the finger at the touch surface. 
     
     
         6 . The touch sensor system of  claim 5 , wherein the scrolling signal is responsive to the non-zero velocity. 
     
     
         7 . The touch sensor system of  claim 3 , wherein the scrolling signal includes a speed component and a direction component, and wherein the scrolling signal is based on the velocity and direction of the finger just prior to lift off. 
     
     
         8 . The touch sensor system of  claim 1 , wherein the touch sensor comprises a two-dimensional capacitive sensor. 
     
     
         9 . The touch sensor system of  claim 6 , wherein the scrolling signal is in quadrature form including characteristics of the type of signals produced by a rotary encoder. 
     
     
         10 . A method for scrolling on a capacitive sensing device of the type including a scroll surface and a capacitive sensor coupled to the scroll surface and configured to measure finger motion, the method comprising:
 generating a scrolling command in response to finger motion at the scroll surface;   ceasing the scrolling command without substantially continuing generating the scrolling command upon the finger lifting from the scroll surface when the finger is stationary immediately prior to lifting from the scroll surface; and   continuing to generate the scrolling command after the finger lifts from the touch surface responsive to finger motion on the scroll surface immediately prior to lifting.   
     
     
         11 . The method of  claim 10 , further comprising simulating friction after the finger lifts from the scroll surface. 
     
     
         12 . The method of  claim 11 , further comprising decaying the scrolling action in response to simulating friction. 
     
     
         13 . The method of  claim 10 , further comprising:
 measuring the instantaneous velocity of the finger at the point the finger lifts off the scrolling surface; and   continuing the scrolling when the instantaneous finger velocity exceeds a predetermined threshold.   
     
     
         14 . The method of  claim 13 , wherein the predetermined velocity is non-zero. 
     
     
         15 . The method of  claim 13 , further comprising adjusting the scrolling behavior based on the finger velocity as the finger lifts away from the scroll surface. 
     
     
         16 . The method of  claim 15 , wherein the coasting speed and direction are proportional to the scrolling speed and direction just before the finger lifts from the scroll surface. 
     
     
         17 . The method of  claim 10 , further comprising stopping the scrolling upon touching the finger back to the scroll surface. 
     
     
         18 . A processing system for use with a capacitive sensor of the type configured to sense a finger along an axis, the processing system configured to:
 generate scrolling in response to finger motion along the axis;   cease the scrolling, without substantially continuing the scrolling, responsive to the finger being substantially stationary immediately prior to lifting from the capacitive sensor; and   continue generating scrolling after the finger lifts from the capacitive sensor to emulate coasting when the finger lift is preceded by finger motion substantially along the axis.   
     
     
         19 . The processing system of  claim 18 , wherein the processing system is further configured to decay scrolling after the finger lift when the finger lift is immediately preceded by finger motion substantially along the axis. 
     
     
         20 . The processing system of  claim 19 , further comprising:
 an enclosure including a layer having an external touch surface and an internal layer, wherein the capacitive sensor is coupled to the internal surface; and   a flexible substrate including a first portion affixed to the capacitive sensor and a second portion spatially separate from the first portion, and wherein the capacitive sensor comprises an array of capacitive sensors disposed on the first portion of the flexible substrate and arranged along the axis.