Method and system for detecting multiple touches on a touch-sensitive screen
First Claim
1. A method for indicating if a set of simultaneous contact points on a touch-sensitive screen contains a plurality of contact points, the method comprising:
- setting a multiple contact point discrimination threshold representing a minimum difference in voltage expected between conductors at opposing edges of the touch-sensitive screen when multiple contact points are presented;
setting a conductor on a first edge of the touch-sensitive screen to a first reference voltage;
setting a conductor on a second edge of the touch-sensitive screen to a second reference voltage, the second edge being across the touch-sensitive screen from the first edge;
taking a first measurement of a voltage associated with a conductor on a third edge of the touch-sensitive screen, the third edge being adjacent to the first and second edges;
taking a second measurement of a voltage associated with a conductor on a fourth edge of the touch-sensitive screen, the fourth edge being adjacent to the first and second edges and across the touch-sensitive screen from the third edge;
comparing the multiple contact point discrimination threshold with a difference between the first and second voltage measurements, the difference reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen; and
if the difference between the first and second voltage measurements is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.
2 Assignments
0 Petitions
Accused Products
Abstract
Disclosed are a method and a system for detecting multiple, simultaneous touches on a touch-sensitive screen of a computing device. The hardware that controls the touch screen performs two measurements to locate a touch location on the screen. If there is a single touch, then the two measurements are equal. A non-zero difference indicates multiple touches and is correlated with the spread of locations simultaneously touched on the screen. If the difference is greater than a set threshold, then an indication is given of multiple touches. The user is warned against multiple touches, and input from the screen is ignored as long as multiple touches are detected. For some embodiments, when multiple touches are detected, the invention also tries to indicate the boundary of the set of locations simultaneously touched. The boundary is used to interpolate the intended single touch from the locations of all the touches.
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Citations
22 Claims
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1. A method for indicating if a set of simultaneous contact points on a touch-sensitive screen contains a plurality of contact points, the method comprising:
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setting a multiple contact point discrimination threshold representing a minimum difference in voltage expected between conductors at opposing edges of the touch-sensitive screen when multiple contact points are presented; setting a conductor on a first edge of the touch-sensitive screen to a first reference voltage; setting a conductor on a second edge of the touch-sensitive screen to a second reference voltage, the second edge being across the touch-sensitive screen from the first edge; taking a first measurement of a voltage associated with a conductor on a third edge of the touch-sensitive screen, the third edge being adjacent to the first and second edges; taking a second measurement of a voltage associated with a conductor on a fourth edge of the touch-sensitive screen, the fourth edge being adjacent to the first and second edges and across the touch-sensitive screen from the third edge; comparing the multiple contact point discrimination threshold with a difference between the first and second voltage measurements, the difference reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen; and if the difference between the first and second voltage measurements is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A computer-readable medium containing computer-executable instruction for performing a method for indicating if a set of simultaneous contact points on a touch-sensitive screen contains a plurality of contact points, the method comprising:
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setting a multiple contact point discrimination threshold representing a minimum difference in voltage expected between conductors at opposing edges of the touch-sensitive when detecting multiple contact points are presented; setting a conductor on a first edge of the touch-sensitive screen to a first reference voltage; setting a conductor on a second edge of the touch-sensitive screen to a second reference voltage, the second edge being across the touch-sensitive screen from the first edge; taking a first measurement of a voltage associated with a conductor on a third edge of the touch-sensitive screen, the third edge being adjacent to the first and second edges; taking a second measurement of a voltage associated with a conductor on a fourth edge of the touch-sensitive screen, the fourth edge being adjacent to the first and second edges and across the touch-sensitive screen from the third edge; comparing the multiple contact point discrimination threshold with a difference between the first and second voltage measurements, the difference reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen; and if the difference between the first and second voltage measurements is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.
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11. A method for indicating if a set of simultaneous contact points on a touch-sensitive screen contains a plurality of contact points, the method comprising:
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setting a multiple contact point discrimination threshold representing a minimum combined difference in voltage expected between pairs of conductors at opposite edges of a touch-sensitive screen when multiple contact points are presented; setting a conductor on a first edge of the touch-sensitive screen to a first reference voltage; setting a conductor on a second edge of the touch-sensitive screen to a second reference voltage, the second edge being across the touch-sensitive screen from the first edge; taking a first measurement of a voltage associated with a conductor on a third edge of the touch-sensitive screen, the third edge being adjacent to the first and second edges; taking a second measurement of a voltage associated with a conductor on a fourth edge of the touch-sensitive screen, the fourth edge being adjacent to the first and second edges and across the touch-sensitive screen from the third edge; setting the conductor on the third edge of thee touch-sensitive screen to a third reference voltage; setting the conductor on the fourth edge of the touch-sensitive screen to a fourth reference voltage; taking a third measurement of a voltage associated with the conductor on the first edge of the touch-sensitive screen; taking a fourth measurement of a voltage associated with the conductor on the second edge of the touch-sensitive screen; combining a first difference between the first and second voltage measurements reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen with a second difference between the third and fourth voltage measurements reflecting a difference in proximity between the set of simultaneous contact points and the first and second edges of the touch-sensitive screen; comparing the multiple contact point discrimination threshold with a combination of the first and second differences; and if the combination of the first and second differences is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A computer-readable medium containing computer-executable instructions for performing a method for indicating if a set of simultaneous contact points on a touch-sensitive screen contains a plurality of contact points, the method comprising;
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setting a multiple con-tact point discrimination threshold; setting a conductor on a first edge of the touch-sensitive screen to a first reference voltage; setting a conductor on a second edge of the touch-sensitive screen to a second reference voltage, the second edge being across the touch-sensitive screen from the first edge; taking a first measurement of a voltage associated with a conductor on a third edge of the touch-sensitive screen, the third edge being adjacent to the first and second edges; taking a second measurement of a voltage associated with a conductor on a fourth edge of the touch-sensitive screen, the fourth edge being adjacent to thee first and second edges and across the touch-sensitive screen from the third edge; setting the conductor on the third edge of the touch-sensitive screen to a third reference voltage; setting the conductor on the fourth edge of the touch-sensitive screen to a fourth reference voltage; taking a third measurement of a voltage associated with the conductor on the first edge of the touch-sensitive screen; taking a fourth measurement of a voltage associated with the conductor on the second edge of the touch-sensitive screen; combining a first difference between the first and second voltage measurements reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen with a second difference between the third and fourth voltage measurements reflecting a difference in proximity between the set of simultaneous contact points and the first and second edges of the touch-sensitive screen; comparing the multiple contact point discrimination threshold with a combination of the first and second differences; and if the combination of the first and second differences is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.
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20. A system for indicating if a set of simultaneous contacts points on a touch-sensitive screen contains a plurality of contact points, the touch-sensitive screen comprising first, second, third, and fourth edges, each edge comprising a conductor, the first edge being across the touch-sensitive screen from the second edge, the third and fourth edges each being adjacent to the first and second edges, and the third edge being across the touch-sensitive screen from the fourth edge, the system comprising:
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a multiple contact paint discrimination threshold representing a minimum combined difference in voltage expected between airs of conductors at opposite edges of a touch-sensitive screen when multiple contact points are presented; a voltage source for setting the first edge conductor to a first reference voltage and for setting the second edge conductor to a second reference voltage; a voltage measurement circuit with an input, and an output; a multiplexor for connecting the input of the voltage measurement circuit alternatively to the third edge conductor and to the fourth edge conductor; a comparator for comparing the multiple contact point discrimination threshold with a difference between a value produced on the output of the voltage measurement circuit when its input is connected to the third edge conductor and a value produced on the output of the voltage measurement circuit when its input is connected to the fourth edge conductor the difference reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen; and an indicator for indicating that the set of simultaneous contacts points on the touch-sensitive screen contains a plurality of contact points, the indicator set based on an output of the comparator.
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21. A system for indicating if a set of simultaneous contacts points on a touch-sensitive screen contains a plurality of contact points, the touch-sensitive screen comprising first, second, third, and fourth edges, each edge comprising a conductor, the first edge being across the touch-sensitive screen from the second edge, the third and fourth edges each being adjacent to the first and second edges with the third edge being across the touch-sensitive screen from the fourth edge, the system comprising:
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a multiple contact point discrimination threshold representing a minimum combined difference in voltage expected between pairs of conductors at opposite edges of a touch-sensitive screen when multiple contact points are presented; a first voltage source for setting the first edge conductor to a first reference voltage and for setting the second edge conductor to a second reference voltage; a first voltage measurement circuit with an input and an output; a first multiplexor for connecting the input of the first voltage measurement circuit alternatively to the third edge conductor and to the fourth edge conductor; a first calculator for calculating a first difference between a value produced on the output of the first voltage measurement circuit when its input is connected to the third edge conductor and a value produced on the output of the first voltage measurement circuit when its input is connected to the fourth edge conductor, the first difference reflecting a difference in proximity between the set of simultaneous contact points and the third and fourth edges of the touch-sensitive screen; a second voltage source for setting the third edge conductor to a third reference voltage and for-setting the fourth edge conductor to a fourth reference voltage; a second voltage measurement circuit with an input and an output; a second multiplexor for connecting the input of the second voltage measurement circuit alternatively to the first edge conductor and to the second edge conductor; a second calculator for calculating a second difference between a value produced on the output of the second voltage measurement circuit when its input is connected to the first edge conductor and a value produced on the output of thee second voltage measurement circuit when its input is connected to the second edge conductor, the second difference reflecting a difference in proximity between the set of simultaneous contact points and the first and second edges of the touch-sensitive screen; a comparator for comparing the multiple contact point discrimination threshold with a combination of the first and second differences; and an indicator for indicating that the set of simultaneous contacts points on the touch-sensitive screen contains a plurality of contact points, the indicator set based on an output of the comparator. - View Dependent Claims (22)
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Specification