Force sensors and touch panels using same

• US 20020180710A1
• Filed: 04/12/2002
• Published: 12/05/2002
• Est. Priority Date: 04/13/2001
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Roberts, Jerry B.
• Granted Patent: US 7,196,694 B2
• Time in Patent Office: Days
• 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 coupling unit coupling between the touch member and the base support, the coupling unit 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 extending between the center portion of the beam member and the peripheral portions of the beam member; and

at least one sensor element disposed to measure a signal indicative of a force at the beam member location due to the force applied to the touch screen.

2. A device as recited in claim 1, wherein the 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, further comprising 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 formed 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.

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

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.

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, further comprising isolating a twisting moment of one of the touch member and an underlying support surface from the other of the touch member and an underlying support surface.

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

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

26. 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.

27. 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.

28. 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.

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

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

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

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

33. A method as recited in claim 32, 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.

34. A method as recited in claim 32, further comprising displaying the image through the touch screen.

35. A method as recited in claim 32, further comprising displaying the image from an image display on the touch screen.

38. A system as recited in claim 37, 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.

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

40. A system as recited in claim 38, wherein the touch panel comprises the display unit.

41. A system as recited in claim 38, further comprising a processor unit coupled to the touch panel controller and the display controller to process information displayed on the display unit and information received from the touch panel controller.

19. A method of detecting the location of a touch on a touch screen having a touch member, comprising:

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.

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

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

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

37. 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 coupling units, at least one of the coupling units coupling between the touch member and the base support, the coupling unit 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 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.

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

a touch member;

a receiving structure;

a force spreading member having a concentrated force receiving region coupled to receive a force passed into the force spreading member from the touch member, and having a force distributing region to pass the force out of the force spreading member to the receiving structure, the force distributing region having a larger area than the force receiving region, the receiving structure and force spreading member being arranged so that changes in curvature of the force spreading member 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 member 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 member.

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

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

45. A device as recited in claim 42, wherein the receiving structure is arranged to prevent contact with the force spreading member proximate the force receiving region, when the force is within the force measurement range.

46. A device as recited in claim 42, wherein the sensing element senses a displacement arising from the force.

47. A device as recited in claim 42, wherein the sensing element is responsive to flexure of the force spreading member.

48. A device as recited in claim 42, wherein the receiving structure includes a cushion of low modulus material contacting the force spreading member proximate the force receiving region.

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

50. A device as recited in claim 42, 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.

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

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

53. A device as recited in claim 51, wherein the touch panel comprises the display.

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

a touch member;

a base support;

a coupling assembly coupled between a coupling region of the touch member and the base support, the coupling assembly being rotationally unconstrained relative to one of the touch member and the base support, the coupling assembly 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 responsive to the force perpendicular to the predominant plane.

55. An assembly as recited in claim 54, 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.

56. An assembly as recited in claim 54, 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.

57. An assembly as recited in claim 54, wherein sensor element produces a detection signal in response to flexure of the beam member.

58. An assembly as recited in claim 54, further comprising a pivot disposed between the touch member and the first region of the beam member.

59. An assembly as recited in claim 54, further comprising a coupling block of relatively low Young'"'"'s modulus material disposed between the touch member and the first region of the beam member.

60. An assembly as recited in claim 54, further comprising a touch controller coupled to receive signals from the force sensing element and to determine a location of a touch on the touch panel.

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

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

63. An assembly as recited in claim 61, wherein the touch member comprises the display.