Force sensors and touch panels using same

• US 7,196,694 B2
• Filed: 04/12/2002
• Issued: 03/27/2007
• Est. Priority Date: 04/13/2001
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Roberts, Jerry B.
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): ABDULSELAM, ABBAS I
• Application Number:
  US10/121,507
• Publication Number:
  US 20020180710A1
• Time in Patent Office: 1,810 Days
• Field of Search: 345173-179, 178 1801- 1808, 341/34, 463/37, 382313-314
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04142 the force sensing means being located peripherally, e.g. disposed at the corners or at the side of a touch sensing plate
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells

Abstract

A touch screen uses one or more force sensors to determine location of the touch on the screen. The force sensor has an accurately determined direction of sensitivity and, therefore, has reduced sensitivity to forces that are non-perpendicular to the screen. The sensor is thin in relation to the area of the active force-sensing element, allowing low profile force touch screens to have a better combination of mechanical integrity, accuracy, sensitivity, and high signal to noise ratio than has heretofore been achieved. The sensor may also be rotationally soft, so that it is effective at preventing twisting motions of the overlay or the support surface from affecting the sensed force.

Claims

1. A device for determining the position of a force applied to a touch screen, comprising:

a touch member;

a base support;

a plurality of coupling units coupled between the touch member and the base support, the coupling units each including a beam member connected at peripheral portions to respective beam member supports, a center portion of the beam member being substantially unsupported relative to the periph&

al portions, a force path passing force between the touch member and the base support, the force path extending between the center portion of the beam member and the peripheral portions of the beam member; and

at least one sensor element associated with each coupling unit and disposed to measure a signal indicative of a force at the beam member location due to the force applied to the touch screen, the position of the force applied to the touch screen being determinable from the sensor element signals.

2. A device as recited in claim 1, wherein each coupling unit includes the at least one sensor element.

3. A device as recited in claim 1, wherein the beam member is elongated in a first direction and the elongated beam member has respective first and second ends at its peripheral portions.

4. A device as recited in claim 1, wherein the beam member is substantially disk-shaped having a disk periphery, and the peripheral portions include portions of the disk periphery.

5. A device as recited in claim 1, wherein each coupling unit further comprises a rotational softener disposed on a first surface of the beam member.

6. A device as recited in claim 5, wherein the rotational softener includes a protruding portion of the first surface of the beam member.

7. A device as recited in claim 5, wherein the rotational softener includes a portion of elastomeric material on the first surface of the beam member.

8. A device as recited in claim 1, wherein the beam member is disposed between the touch member and the beam member supports.

9. A device as recited in claim 8, wherein the beam member supports are integrally formed with the base support.

10. A device as recited in claim 1, wherein the beam member supports are disposed between the touch member and the beam member.

11. A device as recited in claim 10, wherein the beam member supports are integrally fomied with the touch member.

12. A device as recited in claim 1, wherein the at least one sensor element comprises at least one of the beam member supports formed from a force sensitive material.

13. A device as recited in claim 1, wherein the at least one sensor element includes a capacitor formed between the beam member and an electrode on the base support.

14. A device as recited in claim 1, wherein the beam member includes at least a metal surface to form a first plate of the capacitor movable relative to the electrode on the base support.

15. A device as recited in claim 14, wherein the beam member is formed from a metal material.

16. A device as recited in claim 14, wherein the beam member is formed from a non-conducting material upon which is disposed on a surface of the metal material.

17. A device as recited in claim 1, further comprising a lateral softener disposed between the touch member and the base support to permit lateral movement of the touch panel relative to the at least one sensor element.

18. A device as recited in claim 1, wherein the beam member spreads force received from the touch member to the peripheral portions over a distance greater than the thickness of the beam member.

19. A method of detecting the location of a touch on a touch screen having a touch member and an underlying support surface, comprising:

isolating a twisting moment of one of the touch member and the underlying support surface from the other of the touch member and an underlying support surface;

providing a plurality of force-sensitive devices coupled to the touch member, and for each device;

passing at least a portion of a force applied to a first side of the touch member to one of i) a center portion of a force spreader disposed on a second side of the touch member, the center portion of the force spreader being substantially unsupported, and ii) peripheral portions of the force spreader;

spreading the portion of the applied force from the one of the i) the center portion of the force spreader and ii) the peripheral portions of the force spreader to the other of i) the center portion of the force spreader and ii) the peripheral portions of the force spreader; and

measuring a signal indicative of the portion of the applied force passed to the force spreader; and

using the signals measured from each device to determine the touch location.

20. A method as recited in claim 19, further comprising determining the location of the touch on the touch member from the signal measured in the measuring step.

21. A method as recited in claim 19, wherein measuring a signal indicative of the portion of the applied force includes sensing a displacement resulting from the applied force.

22. A method as recited in claim 19, further comprising determining a location of the touch applied to the touch member based on the signal measured in the measuring step.

23. A method as recited in claim 19, wherein isolating the twisting moment includes rotating a rotational bearing disposed between the touch member and the underlying support surface.

24. A method as recited in claim 19, wherein isolating the twisting moment includes rotating an elastomeric bearing disposed between the touch member and the underlying support surface.

25. A method as recited in claim 19, wherein spreading the portion of the applied force includes spreading the portion of the applied force over a distance greater than a thickness of the force spreader.

26. A method as recited in claim 19, wherein measuring a signal indicative of the portion of the applied force includes compressing a force sensitive material and detecting a resulting change in a characteristic of the force sensitive material.

27. A method as recited in claim 19, wherein measuring a signal indicative of the portion of the applied force includes changing capacitance of a capacitor and measuring the change in capacitance.

28. A method as recited in claim 27, wherein the force spreader forms one conductive suiface of the capacitor and changing capacitance of the capacitor includes moving the force spreader relative to a second conductive surface of the capacitor.

29. A method as recited in claim 19, further comprising isolating the force spreader from tangential forces applied to the touch member.

30. A method as recited in claim 29, wherein isolating the force spreader from tangential forces includes disposing a lateral softener between the touch member and an underlying support surface.

31. A method as recited in claim 19, further comprising displaying an image to a user through the touch member.

32. A method as recited in claim 31, further comprising determining a location of a touch on the touch screen and changing the image in response to the determined location of the touch.

33. A method as recited in claim 31, further comprising displaying the image through the touch screen.

34. A method as recited in claim 31, further comprising displaying the image from an image display on the touch screen.

35. A system for detecting the location of a force applied to a first side of a touch member, comprising:

a plurality of force spreading means disposed on a second side of the touch member;

means for passing at least a portion of a force applied to a first side of the touch member to a center portion of each force spreading means, the center portion of each force spreading means being substantially unsupported, each force spreading means passing the portion of the applied force between the center portion and the peripheral portions of each force spreading means; and

means for measuring a signal indicative of the portion of the applied force passed to each force spreading means.

36. A touch panel system for determining the location of a touch on the touch panel, comprising:

a base support;

a touch member coupled to the base support via a plurality of coupling units, each of the coupling units coupling between the touch member and the base support, the coupling units each including;

a beam member connected at peripheral portions to respective beam member supports, a center portion of the beam member being substantially unsupported relative to the peripheral portions, a force path passing force between the touch member and the base support, the force path passing between the center portion of the beam member and the peripheral portions of the beam member; and

at least one sensor element associated with each coupling unit and disposed to measure a signal indicative of a force at the beam member location; and

a touch panel controller coupled to receive signals from the at least one sensor elements and to determine a location of a touch on the touch panel.

37. A system as recited in claim 36, further comprising a display unit disposed to display an image to a user, and a display controller coupled to the display unit to control the image.

38. A system as recited in claim 37, wherein the display unit is disposed below the touch panel and displays the image to the user through the touch member.

39. A system as recited in claim 37, wherein the touch panel comprises the display unit.

40. A system as recited in claim 37, further comprising a processor unit coupled to the touch panel controller and the display controller to process information displayed on the display unit and infonnation received from the touch panel controller.

41. A device for locating the position of a touch on a touch screen, comprising:

a touch member;

a receiving structure;

a plurality of force spreading members each having a concentrated force receiving region coupled to receive a force passed into the force spreading members from the touch member, and each having a force distributing region to pass the force out of the force spreading members to the receiving structure, the force distributing region having a larger area than the force receiving region, the receiving structure and force spreading members being arranged so that changes in curvature of the force spreading members arising from the force maintain loading of the force spreading through the force spreader while the force remains within a measurement range, so as to spread the force within the spreading members to substantially all of the distributing region; and

a sensing element disposed to detect a signal indicative of the force passing through the force spreading members.

42. A device as recited in claim 41, wherein the force receiving region is on a first side of each force spreading member and the force distributing region is on a second side of each force spreading member opposite the first side.

43. A device as recited in claim 42, wherein at least a portion of the force passing through the force spreading members passes in a direction perpendicular to the first and second surfaces.

44. A device as recited in claim 41, wherein the receiving structure is arranged to prevent contact with the force spreading members proximate the force receiving region, when the force is within the force measurement range.

45. A device as recited in claim 41, wherein the sensing element senses a displacement arising from the force.

46. A device as recited in claim 41, wherein the sensing element is responsive to flexure of the force spreading members.

47. A device as recited in claim 41, wherein the receiving structure includes a cushion of low modulus material contacting the force spreading members proximate the force receiving region.

48. A device as recited in claim 47, wherein the receiving structure includes the force sensing element and the force sensing element passes force from the distributing region of the force spreading members to the cushion of low modulus material.

49. A device as recited in claim 41, further comprising a touch controller coupled to receive signals from the sensing element and to determine a location of a touch on the touch panel.

50. A device as recited in claim 49, further comprising a processor connected to receive position information from the touch controller and a display connected to receive display information from the processor.

51. A device as recited in claim 50, wherein the display is disposed below the touch panel to display the information through the touch panel to a viewer.

52. A device as recited in claim 50, wherein the touch panel comprises the display.

53. A system for locating a touch on a touch screen, comprising:

a touch member;

a base support;

a plurality of coupling assemblies coupled between a coupling region of the touch member and the base support, the coupling assemblies being rotationally unconstrained relative to one of the touch member and the base support, the coupling assemblies each including a beam member having a predominant plane, the beam member including a first region coupled to receive force from the touch member, the beam member further including at least one second region, the beam member receiving the force in a direction perpendicular to the predominant plane and passing the force laterally to the at least one second region, the force passing out of the beam member through the at least one second region towards a beam member support of the coupling assembly, and

a sensor element associated with each coupling assembly and responsive to the force perpendicular to the predominant plane.

54. An assembly as recited in claim 53, wherein the sensor element forms part of the beam member support and the sensor element is disposed between the beam member and the base support to receive force from the at least one second region.

55. An assembly as recited in claim 53, wherein the sensor element forms part of the beam member support and the sensor element is disposed between the touch member and the beam member to receive force from the touch member.

56. An assembly as recited in claim 53, wherein sensor element produces a detection signal in response to flexure of the beam member.

57. An assembly as recited in claim 53, wherein each coupling assembly further comprises a pivot disposed between the touch member and the first region of the beam member.

58. An assembly as recited in claim 53, wherein each coupling assembly further comprises a coupling block of relatively low Young'"'"'s modulus material disposed between the touch member and the first region of the beam member.

59. An assembly as recited in claim 53, further comprising a touch controller coupled to receive signals from the force sensing elements and to determine a location of a touch on the touch panel.

60. An assembly as recited in claim 59, further comprising a processor connected to receive position information from the touch controller and a display connected to receive display information from the processor.

61. An assembly as recited in claim 60, wherein the display is disposed below the touch member to display the information through the touch member to a viewer.

62. An assembly as recited in claim 60, wherein the touch member comprises the display.