Multi-touch detection

Abstract

A method for multi-touch detection in a touch input device comprising a grid based sensor, the method comprises sampling outputs from a grid based sensor over a first stage of detection, selecting sensor lines based on the sampled outputs, scanning the selected sensor lines along one axis of the grid based sensor over a second stage of detection, and determining positions of user interaction based on outputs sampled in response to scanning the selected sensor lines during the second stage of detection.

1 . A method for multi-touch detection in a touch input device comprising a grid based sensor, the method comprising:
 sampling outputs from a grid based sensor over a first stage of detection;   selecting sensor lines based on the sampled outputs;   scanning the selected sensor lines along one axis of the grid based sensor over a second stage of detection; and   determining positions of user interaction based on outputs sampled in response to scanning the selected sensor lines during the second stage of detection.   
     
     
         2 . The method according to  claim 1 , wherein the detection during the first and second stage of detection is capacitive based detection. 
     
     
         3 . The method according to  claim 1 , wherein the sensor lines are selected during the first stage of detection in response to determining a presence of user interaction on the sensor lines based on the sampled outputs. 
     
     
         4 . The method according to  claim 1 , wherein the first and second stage of detection is performed over a single refresh cycle of the touch input device. 
     
     
         5 . The method according to  claim 1 , wherein the first stage of detection is shorter in duration than the second stage of detection. 
     
     
         6 . The method according to  claim 5 , comprising selecting one of the first or second axes of the grid based sensor for scanning during the second stage of detection, wherein the selection is based on the number of sensor lines selected on each axis. 
     
     
         7 . The method according to  claim 1 , wherein the sampling during the first stage of detection is in response to simultaneous triggering or interrogating a plurality of sensor lines. 
     
     
         8 . The method according to  claim 1 , wherein the sampling during the first stage of detection is in response to simultaneously triggering all sensor lines along one axis of the grid based sensor. 
     
     
         9 . The method according to  claim 1 , wherein the sampling during the first stage of detection is in response to simultaneously triggering all sensor lines in both axis of the grid based sensor. 
     
     
         10 . The method according to  claim 1 , wherein the sampling during the first stage of detection is in response to simultaneously triggering a first group of sensor lines along a first axis with a first triggering signal and a second group of sensor lines along the first axis with a second triggering signal, wherein the second triggering signal is orthogonal to the first triggering signal. 
     
     
         11 . The method according to  claim 1 , wherein the sampling during the first stage of detection is in response to triggering a plurality of lines along a first axis of the grid based sensor and sampling signals on the second axis of the grid based sensor. 
     
     
         12 . The method according to  claims 1 , wherein the outputs of the sensor lines are sampled simultaneously. 
     
     
         13 . The method according to  claim 1 , wherein the selecting during the first stage of detection is in response to sampling a difference signal between outputs of parallel lines in the grid based sensor. 
     
     
         14 . The method according to  claim 1 , wherein the selecting is in response to detecting a magnitude of an output that is below a threshold value. 
     
     
         15 . The method according to  claim 14 , wherein the threshold is determined in accordance with a baseline level determined in the absence of finger touch. 
     
     
         16 . The method according to  claim 1 , wherein the selecting comprises selecting sensor lines along both axes of the grid based sensor. 
     
     
         17 . The method according to  claim 1 , comprising selecting sensor lines neighboring the selected lines and including the selected lines as part of the selected lines triggered during the second stage of detection. 
     
     
         18 . The method according to  claim 1 , comprising choosing a pre-determined number of sensor lines from the selected lines and triggering only the pre-determined number of selected sensor lines chosen during the second stage of detection. 
     
     
         19 . The method according to  claim 18 , wherein the selected sensor lines associated with a most pronounced detection signal from all the selected sensor lines are chosen. 
     
     
         20 . The method according to  claim 18 , comprising transmitting the coordinates to a host associated with the touch input device. 
     
     
         21 . The method according to  claim 1 , wherein the outputs indicating a presence of user interaction is in response to at least one of touch and hovering of the user interaction. 
     
     
         22 . The method according to  claim 1 , wherein the user interaction is a fingertip. 
     
     
         23 . The method according to  claim 1 , wherein different detection methods are used for the different stages of detection. 
     
     
         24 . The method according to  claim 1 , wherein during the first stage of detection, the sensor lines are identified based on a one-dimensional detection method for detecting user interaction. 
     
     
         25 . The method according to  claim 1 , wherein during the first stage of detection, the sensor lines are identified based on a single touch detection method. 
     
     
         26 . The method according to  claim 1 , wherein during the second stage of detection, determining coordinates of user interaction is based on a two-dimensional detection method for detecting user interaction. 
     
     
         27 . The method according to  claim 1 , wherein during the second stage of detection, determining coordinates of user interactions is based on a multi-touch detection method. 
     
     
         28 . A method for multi-touch detection in a touch input device comprising a grid based sensor, the method comprising:
 performing a first touch detection during a first detection stage, wherein the first touch detection provides for selecting sensor lines on both axes of the grid based sensor affected by user interaction with the sensor;   determining if coordinates of the user interactions are ambiguous based on the first touch detection during the first detection stage; and   performing a second touch detection that provides for determining junctions affected by user interaction during a subsequent detection stage during a same refresh cycle in response to determined ambiguity, to resolve the ambiguity.   
     
     
         29 . The method according to  claim 28 , wherein the first and second touch detection is a capacitive based detection. 
     
     
         30 . The method according to  claim 28 , wherein the first and second detection stage is performed over a single refresh cycle of the touch input device. 
     
     
         31 . The method according to  claim 28 , comprising skipping the second stage of detection during at least one refresh cycle in response to no sensor lines selected during the first detection stage of the cycle. 
     
     
         32 . The method according to  claim 28 , comprising skipping the second stage of detection during at least one refresh cycle in response to only selecting sensor lines associated with a single interaction location during the first stage of detection of the cycle. 
     
     
         33 . The method according to  claim 28 , comprising skipping the second stage of detection of at least one refresh cycle in response to selecting sensor lines during the refresh cycle that is substantially similar to the sensor lines identified during refresh cycle directly preceding the current refresh cycle. 
     
     
         34 . The method according to  claim 33 , comprising determining coordinates of user interactions based on tracking information from previous refresh cycles. 
     
     
         35 . A method for touch detection in a touch input device comprising a grid based sensor, the method comprising:
 simultaneously triggering a plurality of sensor lines along a first axis of a grid based sensor with a same triggering signal;   sampling capacitively coupled signals on the second axis of the grid based sensor in response to the triggering;   simultaneously triggering a plurality of sensor lines along the second axis of the grid based sensor with a same triggering signal;   sampling capacitively coupled signals on the first axis in response to the sampling; and   determining sensor lines on the first and second axis that have output that indicate a presence of a user interaction.   
     
     
         36 . The method according to  claim 35 , wherein the capacitively coupled signals are sampled substantially simultaneously. 
     
     
         37 . The method according to  claim 35 , comprising simultaneously triggering a first group of sensor lines with a first triggering signal and a second group of sensor lines with a second triggering signal, wherein the second triggering signal is orthogonal to the first triggering signal. 
     
     
         38 . The method according to  claim 37 , wherein the first and second triggering signals are orthogonal in phase. 
     
     
         39 . The method according to  claim 37 , wherein the first and second triggering signals are orthogonal in frequency. 
     
     
         40 . The method according to  claim 35 , comprising simultaneously triggering a first group of sensor lines along an axis and subsequently triggering a second group of sensor lines along the axis. 
     
     
         41 . The method according to  claim 35 , wherein determining sensor lines on the first and second axis that have output that indicate a presence of a user interaction is in response to detecting a magnitude of an output that is below a threshold value. 
     
     
         42 . The method according to  claim 41 , wherein the threshold is determined in accordance with a baseline level determined in the absence of finger touch. 
     
     
         43 . A method of multi-touch detection in a touch input device comprising:
 identifying regions in which may have interactions in a first detection stage;   scanning only the identified regions in a second detection stage to localize the position of the interactions, wherein the first and second stage are performed during a single refresh cycle.