Method and system for detecting multiple touches on a touch-sensitive screen

• US 20040001048A1
• Filed: 06/28/2002
• Published: 01/01/2004
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kraus, Mark Gerard, Nguyen, Vu Xuan
• Granted Patent: US 7,023,427 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04808 Several contacts: gestures triggering a specific function, e.g. scrolling, zooming, right-click, when the user establishes several contacts with the surface simultaneously; e.g. using several fingers or a combination of fingers and pen
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text

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.

Claims

1. A method for indicating that 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;

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;

comparing the multiple contact point discrimination threshold with a difference between the first and second measurements; and

if the difference between the first and second 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. The method of claim 1 wherein the set of simultaneous contact points consists of a single contact point.

3. The method of claim 1 wherein the multiple contact point discrimination threshold is set to zero.

4. The method of claim 1 wherein setting a multiple contact point discrimination threshold comprises considering a request regarding a value for the threshold from a program configured to receive input from the touch-sensitive screen.

5. The method of claim 1 further comprising:

if the difference between the first and second measurements is not greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a single contact point.

6. The method of claim 1 further comprising:

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;

comparing the multiple contact point discrimination threshold with a difference between the third and fourth measurements; and

if the difference between the third and fourth 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.

7. The method of claim 6 further comprising:

if the difference between the third and fourth measurements is not greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a single contact point.

8. The method of claim 6 wherein the first reference voltage equals the third reference voltage and wherein the second reference voltage equals the fourth reference voltage.

9. The method of claim 1 further comprising increasing the multiple contact point discrimination threshold in response to finding that the difference between the first and second measurements is greater than the multiple contact point discrimination threshold.

10. A computer-readable medium containing computer-executable instructions for performing a method for indicating that 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;

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;

comparing the multiple contact point discrimination threshold with a difference between the first and second measurements; and

if the difference between the first and second 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.

11. A method for indicating that 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;

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;

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 measurements with a second difference between the third and fourth measurements;

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.

12. The method of claim 11 wherein the set of simultaneous contact points consists of a single contact point.

13. The method of claim 11 wherein the multiple contact point discrimination threshold is set to zero.

14. The method of claim 11 wherein setting a multiple contact point discrimination threshold comprises considering a request regarding a value for the threshold from a program configured to receive input from the touch-sensitive screen.

15. The method of claim 11 wherein the first reference voltage equals the third reference voltage and wherein the second reference voltage equals the fourth reference voltage.

16. The method of claim 11 wherein combining the first and second differences comprises taking a sum of a square of the first difference and a square of the second difference.

17. The method of claim 11 further comprising:

if the combination of the first and second differences is not greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a single contact point.

18. The method of claim 11 further comprising increasing the multiple contact point discrimination threshold in response to finding that the combination of the first and second differences is greater than the multiple contact point discrimination threshold.

19. A computer-readable medium containing computer-executable instructions for performing a method for indicating that 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;

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;

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 measurements with a second difference between the third and fourth measurements;

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.

20. A method for indicating that 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;

at locations along a first edge of the touch-sensitive screen, sending probes across the touch-sensitive screen;

at locations along a second edge of the touch-sensitive screen, attempting to detect probes sent across the touch-sensitive screen, the second edge being across the touch-sensitive screen from the first edge;

of a set of locations along the second edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, storing a first location in the set that is at least as close to a third edge of the touch-sensitive screen as any other location in the set, and storing a second location in the set that is at least as close to a fourth edge of the touch-sensitive screen as any other location in the set, the third and fourth edges each being adjacent to the first and second edges;

comparing the multiple contact point discrimination threshold with a distance between the first and second locations; and

if the distance between the first and second locations is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.

21. The method of claim 20 wherein the set of simultaneous contact points consists of a single contact point and wherein the first and second locations are the same location.

22. The method of claim 20 wherein the multiple contact point discrimination threshold is set to zero.

23. The method of claim 20 wherein setting a multiple contact point discrimination threshold comprises considering a request regarding a value for the threshold from a program configured to receive input from the touch-sensitive screen.

24. The method of claim 20 wherein sending probes comprises sending waves selected from the group consisting of:

acoustic waves and infrared light waves.

25. The method of claim 24 wherein detecting a probe in an altered states comprises detecting a wave with a reduced amplitude.

26. The method of claim 20 wherein indicating comprises indicating the first and second locations.

27. The method of claim 20 further comprising:

if the distance between the first and second locations is not greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a single contact point.

28. The method of claim 20 further comprising:

at locations along the third edge, sending probes across the touch-sensitive screen;

at locations along the fourth edge, attempting to detect probes sent across the touch-sensitive screen;

of a set of locations along the fourth edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, storing a third location in the set that is at least as close to the first edge as any other location in the set, and storing a fourth location in the set that is at least as close to the second edge as any other location in the set;

comparing the multiple contact point discrimination threshold with a distance between the third and fourth locations; and

if the distance between the third and fourth locations is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.

29. The method of claim 28 wherein indicating comprises indicating the third and fourth locations.

30. The method of claim 28 further comprising:

if the distance between the third and fourth locations is not greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a single contact point.

31. The method of claim 20 further comprising increasing the multiple contact point discrimination threshold in response to finding that the distance between the first and second locations is greater than the multiple contact point discrimination threshold.

32. A computer-readable medium containing computer-executable instructions for performing a method for indicating that 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;

at locations along a first edge of the touch-sensitive screen, sending probes across the touch-sensitive screen;

at locations along a second edge of the touch-sensitive screen, attempting to detect probes sent across the touch-sensitive screen, the second edge being across the touch-sensitive screen from the first edge;

of a set of locations along the second edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, storing a first location in the set that is at least as close to a third edge of the touch-sensitive screen as any other location in the set, and storing a second location in the set that is at least as close to a fourth edge of the touch-sensitive screen as any other location in the set, the third and fourth edges each being adjacent to the first and second edges;

comparing the multiple contact point discrimination threshold with a distance between the first and second locations; and

if the distance between the first and second locations is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.

33. A method for indicating that 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;

at locations along a first edge of the touch-sensitive screen, sending probes across the touch-sensitive screen;

at locations along a second edge of the touch-sensitive screen, attempting to detect probes sent across the touch-sensitive screen, the second edge being across the touch-sensitive screen from the first edge;

of a set of locations along the second edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, storing a first location in the set that is at least as close to a third edge of the touch-sensitive screen as any other location in the set, and storing a second location in the set that is at least as close to a fourth edge of the touch-sensitive screen as any other location in the set, the third and fourth edges each being adjacent to the first and second edges;

computing a first distance between the first and second locations;

at locations along the third edge, sending probes across the touch-sensitive screen;

at locations along the fourth edge, attempting to detect probes sent across the touch-sensitive screen;

of a set of locations along the fourth edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, storing a third location in the set that is at least as close to the first edge as any other location in the set, and storing a fourth location in the set that is at least as close to the second edge as any other location in the set;

computing a second distance between the third and fourth locations;

comparing the multiple contact point discrimination threshold with a combination of the first and second distances; and

if the combination of the first and second distances is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.

34. The method of claim 33 wherein the set of simultaneous contact points consists of a single contact point;

wherein the first and second locations are the same location; and

wherein the third and fourth locations are the same location.

35. The method of claim 33 wherein the multiple contact point discrimination threshold is set to zero.

36. The method of claim 33 wherein setting a multiple contact point discrimination threshold comprises considering a request regarding a value for the threshold from a program configured to receive input from the touch-sensitive screen.

37. The method of claim 33 wherein sending probes comprises sending waves selected from the group consisting of:

acoustic waves and infrared light waves.

38. The method of claim 37 wherein detecting a probe in an altered states comprises detecting a wave with a reduced amplitude.

39. The method of claim 33 wherein the combination of the first and second distances comprises a sum of a square of the first distance and a square of the second distance.

40. The method of claim 33 wherein indicating comprises indicating the first, second, third, and fourth locations.

41. The method of claim 33 further comprising:

if the combination of the first and second distances is not greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a single contact point.

42. The method of claim 33 further comprising increasing the multiple contact point discrimination threshold in response to finding that the combination of the first and second distances is greater than the multiple contact point discrimination threshold.

43. A computer-readable medium containing computer-executable instructions for performing a method for indicating that 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;

at locations along a first edge of the touch-sensitive screen, sending probes across the touch-sensitive screen;

at locations along a second edge of the touch-sensitive screen, attempting to detect probes sent across the touch-sensitive screen, the second edge being across the touch-sensitive screen from the first edge;

of a set of locations along the second edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, storing a first location in the set that is at least as close to a third edge of the touch-sensitive screen as any other location in the set, and storing a second location in the set that is at least as close to a fourth edge of the touch-sensitive screen as any other location in the set, the third and fourth edges each being adjacent to the first and second edges;

computing a first distance between the first and second locations;

at locations along the third edge, sending probes across the touch-sensitive screen;

at locations along the fourth edge, attempting to detect probes sent across the touch-sensitive screen;

of a set of locations along the fourth edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, storing a third location in the set that is at least as close to the first edge as any other location in the set, and storing a fourth location in the set that is at least as close to the second edge as any other location in the set;

computing a second distance between the third and fourth locations;

comparing the multiple contact point discrimination threshold with a combination of the first and second distances; and

if the combination of the first and second distances is greater than the multiple contact point discrimination threshold, then indicating that the set of simultaneous contact points contains a plurality of contact points.

44. A system for indicating that 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, the system comprising:

a multiple contact point discrimination threshold;

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; 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.

45. A system for indicating that 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, the system comprising:

a multiple contact point discrimination threshold;

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;

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 the second voltage measurement circuit when its input is connected to the second edge conductor;

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.

46. The system of claim 45 wherein the first and second voltage sources are the same voltage source;

wherein the first and second voltage measurement circuits are the same voltage measurement circuit;

wherein the first and second multiplexors are the same multiplexor; and

wherein the first and second calculators are the same calculator.

47. A system for indicating that 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, 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, the system comprising:

a multiple contact point discrimination threshold;

a transmitter for sending probes from locations along the first edge across the touch-sensitive screen;

a detector for detecting probes received along locations on the second edge;

a memory for storing a first location and a second location from a set of locations along the second edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, the first location being at least as close to the third edge as any other location in the set, the second location being at least as close to the fourth edge as any other location in the set;

a comparator for comparing the multiple contact point discrimination threshold with a distance between the first and second locations; 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.

48. A system for indicating that 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, 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, the system comprising:

a multiple contact point discrimination threshold;

a first transmitter for sending probes from locations along the first edge across the touch-sensitive screen;

a first detector for detecting probes received along locations on the second edge;

a first memory for storing a first location and a second location from a set of locations along the second edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, the first location being at least as close to the third edge as any other location in the set, the second location being at least as close to the fourth edge as any other location in the set;

a second transmitter for sending probes from locations along the third edge across the touch-sensitive screen;

a second detector for detecting probes received along locations on the fourth edge;

a second memory for storing a third location and a fourth location from a set of locations along the fourth edge where attempts to detect probes fail to detect a probe or that detect a probe in an altered state, the third location being at least as close to the first edge as any other location in the set, the fourth location being at least as close to the second edge as any other location in the set;

a comparator for comparing the multiple contact point discrimination threshold with a combination of a first distance and a second distance, the first distance being a distance between the first location and the second location, the second distance being a distance between the third location and the fourth location; 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.

49. In a computing system comprising a touch-sensitive screen, a method for responding to an indication that a set of simultaneous contact points on the touch-sensitive screen contains a plurality of contact points, the method comprising:

setting a multiple contact point discrimination threshold;

receiving an indication that a set of simultaneous contact points on the touch-sensitive screen contains a plurality of contact points; and

discarding input from the touch-sensitive screen until receiving an indication that a set of simultaneous contact points on the touch-sensitive screen contains a single contact point.

50. The method of claim 49 wherein the multiple contact point discrimination threshold is set based upon a characteristic selected from the group consisting of:

a type of program configured to receive input from the touch-sensitive screen and a type of physical stylus.

51. The method of claim 49 wherein receiving an indication that a set of simultaneous contact points on the touch-sensitive screen contains a plurality of contact points comprises receiving an indication of a boundary of the set of simultaneous contact points.

52. The method of claim 51 wherein receiving an indication of a boundary comprises receiving a value selected from the group consisting of:

a leftmost contact point location, a rightmost contact point location, a topmost contact point location, and a bottommost contact point location.

53. The method of claim 51 further comprising:

after receiving an indication of a boundary and before discarding input from the touch-sensitive screen, interpolating a contact point on the touch-sensitive screen from a former single contact point and from the indicated boundary; and

treating the interpolated contact point as a single contact point on the touch-sensitive screen.

54. The method of claim 53 wherein interpolating a contact point comprises selecting a top-left corner of the indicated boundary as the single contact point.

55. The method of claim 49 further comprising posting a warning against touching the touch-sensitive screen, the warning selected from the group consisting of:

a visual warning displayed on the touch-sensitive screen and an audible warning.

56. A computer-readable medium containing computer-executable instructions for performing, in a computing system comprising a touch-sensitive screen, a method for responding to an indication that a set of simultaneous contact points on the touch-sensitive screen contains a plurality of contact points, the method comprising:

setting a multiple contact point discrimination threshold;

receiving an indication that a set of simultaneous contact points on the touch-sensitive screen contains a plurality of contact points; and

discarding input from the touch-sensitive screen until receiving an indication that a set of simultaneous contact points on the touch-sensitive screen contains a single contact point.