Touch screen with rotationally isolated force sensor

• US 20020163509A1
• Filed: 04/12/2002
• Published: 11/07/2002
• 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 7,190,350 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. Bending or twisting of the touch screen overlay, or of the support structure upon which the touch screen is mounted, may result in the detection of undesirable forces by force sensors. These undesirable forces may distort the measurement of the location of the touch on the screen. The force sensor is arranged to reduce the effects of flexure on the determination of the location of the touch. For example, a rotational softener, such as a rotational bearing or a pliable material may be included with the force sensor.

Claims

1. A device for determining the location of a touch on a touch screen, comprising:

a flexible touch member movable in response to the touch;

a support structure;

a plurality of sensor units coupled between the support structure and the touch member at respective sensor regions of the touch member, the sensor units measuring a signal indicative of a force due to the touch that is passed through the sensor regions, at least a first sensor unit of the plurality of force sensor units being arranged so that twisting of one of the touch member and the support structure passes substantially no moment through the first sensor unit.

2. A device as recited in claim 1, wherein the first sensor unit couples to the touch member at a position between the support structure and a touch plane of the touch member.

3. A device as recited in claim 1, wherein the touch member is rotatable relative to the support structure about a rotation axis proximate the first sensor unit.

4. A device as recited in claim 3, wherein the rotation axis is positioned below the touch member.

5. A device as recited in claim 3, wherein the rotation axis is positioned closer to a center of the first sensor unit than to a touch surface of the touch member.

6. A device as recited in claim 1, wherein the sensor unit includes a rotational bearing coupled between the touch member and the support structure to allow relative rotation between the touch member and the support structure.

7. A device as recited in claim 6, wherein the sensor unit further includes at least one receptacle to maintain a lateral position of the rotational bearing.

8. A device as recited in claim 6, further comprising a force spreader disposed between the rotational bearing and a force sensing element to spread the force received through the rotational bearing on the force sensing element.

9. A device as recited in claim 1, wherein the sensor unit includes a coupling having a narrowed portion that permits rotation of one part of the coupling on a first side of the narrowed portion relative to a second part of the coupling on a second side of the narrowed portion.

10. A device as recited in claim 1, wherein the sensor unit includes a coupling of low modulus material.

11. A device as recited in claim 10, wherein the coupling of low modulus material is formed from an elastomer.

12. A device as recited in claim 10, wherein the coupling of low modulus is a foam.

13. A device as recited in claim 1, wherein the sensor unit includes a sensing element that is responsive to shear, a line of force between the touch member and the support structure being substantially parallel to a touch plane of the touch member.

14. A device as recited in claim 1, wherein at least one of the plurality of sensor units includes a capacitive force sensing element.

15. A device as recited in claim 14, wherein the capacitive force sensing element includes a spring member separated from an electrode by a gap separation, the extent of the gap separation being dependent on a magnitude of a force applied through the sensor unit.

16. A device as recited in claim 14, wherein the capacitive force sensing element includes a bearing that is rotationally free in at least one direction.

17. A device as recited in claim 16, wherein the bearing is a protruding portion of a spring member of the capacitive force sensing element.

18. A device as recited in claim 1, further comprising a lateral softener disposed on a force path that transmits force through at least one of the sensor units from the touch member to the support structure.

19. A device as recited in claim 1, further comprising a display unit disposed below the touch member to display an image through the touch member.

20. A device as recited in claim 19, further comprising a processing unit coupled to display information via the display unit and receive information via the plurality of sensor units.

21. A device as recited in claim 1, wherein the touch member includes a display unit.

22. A method of locating a touch on a flexible touch surface, comprising:

measuring a signal indicative of a force passing through a sensor unit due the touch while isolating a twisting moment of one of the touch surface and a support structure from the other of the touch surface and the support structure.

23. A method as recited in claim 22, wherein isolating the twisting moment includes isolating the twisting moment with a rotational bearing.

24. A method as recited in claim 23, further comprising constraining lateral movement of the rotational bearing.

25. A method as recited in claim 23, further comprising laterally spreading a force received through the rotational bearing.

26. A method as recited in claim 22, wherein isolating the twisting moment includes bending a coupling at a narrowed portion of the coupling.

27. A method as recited in claim 22, wherein isolating the twisting moment includes deforming a bearing formed from a low modulus material.

28. A method as recited in claim 27, wherein the low modulus material is an elastomer.

29. A method as recited in claim 27, wherein the low modulus material is a foam.

30. A method as recited in claim 22, wherein sensing the movement of the touch screen includes shearing a sensing element in the sensor unit.

31. A method as recited in claim 22, wherein measuring a signal indicative of the force passing through the sensor unit due to the touch includes compressing a sensing element in the sensor unit.

32. A method as recited in claim 22, wherein measuring a signal indicative of the force passing through the sensor unit due to the touch includes moving a first conductive surface of a capacitor relative to a second conductive surface of the capacitor and measuring a change in capacitance.

33. A method as recited in claim 22, further comprising permitting the touch surface to move laterally relative to the sensor unit.

34. A method as recited in claim 22, wherein the measured signal is derived from a displacement in the sensor unit.

35. A method as recited in claim 22, further comprising displaying an image through the flexible touch screen.

36. A method as recited in claim 22, wherein the flexible touch screen includes an image display device, and further comprising displaying an image using the image display device.

39. A device as recited in claim 38, wherein the first sensor unit couples to the touch member at a position between the support structure and a touch plane of the touch member.

40. A device as recited in claim 38, wherein the touch member is rotatable relative to the support structure about a rotation axis proximate the first sensor unit.

41. A device as recited in claim 38, wherein at least one of the sensor units includes a rotational bearing coupled between the touch member and the support structure to allow relative rotation between the touch member and the support structure.

42. A device as recited in claim 41, wherein the at least one of the sensor units further includes at least one receptacle to maintain a lateral position of the rotational bearing.

43. A device as recited in claim 38, wherein at least one of the sensor units includes a coupling having a narrowed portion that permits rotation of one part of the coupling on a first side of the narrowed portion relative to a second part of the coupling on a second side of the narrowed portion.

44. A device as recited in claim 38, wherein at least one of the sensor units includes a coupling of low modulus material.

45. A device as recited in claim 38, wherein at least one of the sensor units includes a sensing element that is responsive to shear, a line of force between the touch member and the support structure being substantially parallel to a touch plane of the touch member.

46. A device as recited in claim 38, wherein at least one of the sensor units includes a capacitive force sensing element.

47. A device as recited in claim 46, wherein the capacitive force sensing element includes a spring member separated from an electrode by a gap separation, the extent of the gap separation being dependent on a magnitude of a force applied through the sensor unit.

48. A device as recited in claim 47, wherein the spring member includes a protruding portion to form a rotational bearing.

49. A device as recited in claim 38, further comprising a display unit disposed below the touch member to display an image through the touch member.

50. A device as recited in claim 49, further comprising a processing unit coupled to display information via the display unit and receive information via the plurality of force sensor units.

51. A device as recited in claim 38, wherein the touch member includes a display unit.

37. A touch sensitive device for locating the position of a touch force, comprising;

a flexible touch member;

means for measuring signals indicative of forces passing through sensor regions due to arising from displacement of the touch member relative to a support due to the touch force; and

means for isolating a twisting moment at the sensor regions of one of the touch member and the support from the other of the touch member and the support.

38. A touch sensitive device for locating the position of a touch, comprising:

a flexible touch member movable in response to an applied force;

a support structure;

a plurality of sensor units coupled between the support structure and the touch member at respective sensor regions of the touch member, the sensor units measuring a signal indicative of a force due to the touch that is passed through the sensor regions, wherein substantially the same relative pattern of internal stresses being developed in a first sensor unit of the plurality of sensor units irrespective of a location of the touch upon the touch member.