Position sensor

• US 20020179339A1
• Filed: 03/28/2002
• Published: 12/05/2002
• Est. Priority Date: 05/14/1994
• Status: Active Grant

• Current Assignee: Synaptics (UK) Ltd. (Synaptics Incorporated)
• Original Assignee: Synaptics (UK) Ltd. (Synaptics Incorporated)
• Inventors: Ely, David T.E., Dames, Andrew N.
• Granted Patent: US 6,888,538 B2
• Time in Patent Office: Days
• US Class Current: 178/18.07
• CPC Class Codes: G01D 5/2073 by movement of a single coil with respect to two or more coils
• CPC Class Codes: G01D 5/208 using polyphase currents
• CPC Class Codes: G06F 1/1626 with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]
• CPC Class Codes: G06F 1/1643 the display being associated to a digitizer, e.g. laptops that can be used as penpads details related to the relative motion of the display enclosure with respect to the body enclosure, e.g. to move between laptop and tablet PC configuration G06F1/1615
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

A low cost x-y digitising system is provided for use in consumer electronic devices, such as portable digital assistants, mobile telephones, web browsers and the like. The digitiser includes a resonant stylus, an excitation winding for energising the resonant stylus and a set of sensor windings for sensing the signal generated by the stylus, from which the x-y position of the stylus is determined.

Claims

1. A winding for use in a position detector, the winding comprising at least two sets of loops which are arranged in succession along a measurement direction with each loop comprising a plurality of primary conductors which cross the measurement direction and a plurality of connecting conductors which extend along the measurement direction for connecting the primary conductors to each other;

and

wherein the loops of the at least two sets of loops are connected in series with each other by a plurality of cross connections between the primary conductors of adjacent loops.

2. A winding according to claim 1, wherein said cross connections are provided in a central portion of said primary conductors.

4. A winding according to any preceding claim, wherein said conductors are formed by conductor tracks on an insulator base which extends along said measurement direction.

5. A winding according to claim 4, wherein said conductors are formed by a plurality of conductor tracks on a printed circuit board.

6. A winding according to claim 5, wherein said printed circuit board is a two layer printed circuit board.

7. A winding according to any preceding claim, wherein the loops of said at least two sets of loops are arranged so that EMFs induced in loops of the same set by a common background alternating magnetic field add together and so that EMFs induced in the loops of one set by a common background alternating magnetic field oppose the EMFs induced in the loops of the other set.

8. A winding according to any preceding claim, wherein each set of loops comprises the same number of loops.

9. A winding according to any preceding claim, wherein each set of loops is arranged to enclose substantially the same area.

10. A winding according to any preceding claim, wherein said primary conductors are arranged with decreasing and increasing density along said measurement direction.

11. A winding according to claim 10, wherein the spacing between adjacent primary conductors varies in a sinusoidal manner along said measurement direction.

13. An apparatus according to claim 12, wherein said conductors are formed by a plurality of conductor tracks on a printed circuit board.

14. An apparatus according to claim 13, wherein said printed circuit board is a flexible printed circuit board.

16. An apparatus according to claim 15, wherein the loops of said at least two sets of loops of said first and second windings are arranged so that EMFs induced in loops of the same set by a common background alternating magnetic field add together and so that EMFs induced in the loops of one set by a common background alternating magnetic field oppose the EMFs induced in the loops of the other set.

17. An apparatus according to claim 15 or 16, wherein each set of loops comprises the same number of loops.

21. An apparatus according to claim 19, wherein the spacing between the primary conductors of said first winding varies in a sinusoidal manner along said x-direction.

64. A method of detecting the position of first and second members which are relatively moveable along a measurement path, the method comprising the steps of:

providing a winding according to any of claims 1 to 11 or an apparatus according to any of claims 12 to 43 on one of said first and second members;

providing a magnetic field generator on the other member;

generating a magnetic field with said generator; and

detecting the generated magnetic field with said winding or said apparatus and determining therefrom the relative position of said first and second members.

65. A method of detecting the position of first and second members which are relatively moveable along a measurement path, the method comprising the steps of:

providing a winding according to any of claims 1 to 11 or an apparatus according to any of claims 12 to 43 on one of said first and second members;

providing a magnetic field detector on the other member;

generating a magnetic field with said winding or said apparatus; and

detecting the generated magnetic field with said magnetic field detector and determining therefrom the relative position of said first and second members.

68. The combination of a winding according to any of claims 1 to 11 and a stylus according to any of claims 44 to 61.

70. A portable data input/output device comprising a winding according to any of claims 1 to 11 or an apparatus according to any of claims 12 to 43.

71. A portable data input/output device comprising a winding according to any of claims 1 to 11 or an apparatus according to any of claims 12 to 43 and a stylus according to any of claims 44 to 61.

72. A device according to claim 70 or 71, further comprising a display and wherein said winding or apparatus is located behind the display.

74. A device according to any of claims 70 to 73, wherein said device is a personal digital assistant.

75. A device according to any of claims 70 to 73, wherein said device is a mobile telephone.

3. A winding for use in a position detector, the winding comprising at least two sets of loops which are arranged in succession along a measurement direction, with each set of loops comprising an outer loop, an inner loop and at least one intermediate loop;

wherein each loop comprises a plurality of primary conductors which cross the measurement direction and a plurality of connecting conductors which extend along the measurement direction for connecting the primary conductors to each other; and

wherein the connecting conductors for the inner loop are located between the connecting conductors for at least one of the intermediate loops and the connecting conductors for the outer loop.

12. An apparatus for use in an x-y position detector, the apparatus comprising:

a first winding which extends substantially over an entire measurement area of the x-y position detector;

a second winding which extends substantially over the entire measurement area of the x-y position detector;

wherein said first and second windings are formed by a plurality of conductors which are formed on two sides of an insulator base and which are connected through the base where appropriate;

wherein the conductors of the first winding include a plurality of primary conductors which extend substantially in said y-direction and which are arrayed over said measurement area and a plurality of connecting conductors which extend substantially in said x-direction at the sides of said measurement area which extend in said x-direction;

wherein the conductors of the second winding include a plurality of primary conductors which extend substantially in said x-direction and which are arrayed over said measurement area and a plurality of connecting conductors which extend substantially in said y-direction at the sides of said measurement area which extend in said y-direction; and

wherein the connecting conductors of the first winding are arranged to be closer to a central portion of said measurement area than the outermost primary conductors of the second winding.

15. An apparatus according to any of claims 12 to 14, wherein the conductors of said first winding are arranged to form at least two sets of loops which are arranged in succession along the x-direction and wherein the conductors of said second winding are arranged to form at least two sets of loops which are arranged in succession along the y-direction.

18. An apparatus according to any of claims 15 to 17, wherein each set of loops is arranged to enclose substantially the same area.

19. An apparatus according to any of claims 12 to 18, wherein the primary conductors of said first winding are arranged with decreasing and increasing density along said x-direction.

20. An apparatus according to any of claims 12 to 19, wherein the primary conductors of said second winding are arranged with decreasing and increasing density along said y-direction.

22. An apparatus according to claim 20, wherein the spacing between the primary conductors of said second winding varies in a sinusoidal manner along said y-direction.

23. An apparatus according to any of claims 12 to 22, further comprising third and fourth windings which extend substantially over the entire measurement area of the x-y position detector,

wherein said third and fourth windings are formed by a plurality of conductors which are formed on the two sides of said insulator base and which are connected through the base where appropriate;

wherein the conductors of the third winding include a plurality of primary conductors which extend substantially in said y-direction and which are arrayed over said measurement area and a plurality of connecting conductors which extend substantially in said x-direction at the sides of said measurement area which extend in said x-direction;

wherein the conductors of the fourth winding include a plurality of primary conductors which extend substantially in said x-direction and which are arrayed over said measurement area and a plurality of connecting conductors which extend substantially in said y-direction at the sides of said measurement area which extend in said y-direction.

24. An apparatus according to claim 23, wherein the connecting conductors of the third winding are closer to the central portion of the measurement area than the outermost primary windings of said second winding.

25. An apparatus according to claim 23 or 24, wherein the connecting conductors of the third winding are closer to the central portion of the measurement area than the outermost primary windings of said fourth winding.

26. An apparatus according to an of claims 12 to 25, wherein most of the conductors which extend in said x-direction are formed on one side of said insulator base and most of said conductors which extend in said y-direction are formed on the other side of said insulator base.

27. An apparatus according to any of claims 12 to 26, further comprising a winding which comprises a plurality of turns of conductor which are wound around the periphery of said insulator base.

29. An apparatus according to claim 27, wherein said first and second windings are formed on two sides of an insulator base and which are connected through the base where appropriate.

30. An apparatus according to claim 29, wherein said conductors are formed by a plurality of conductor tracks on a printed circuit board.

34. An apparatus according to any of claims 12 to 18, wherein the primary conductors of said second winding are arranged with decreasing and increasing density along said measurement direction.

69. The combination of an apparatus according to any of claims 12 to 43 and a stylus according to any of claims 44 to 61.

28. An apparatus for use in a position detector, the apparatus comprising:

a first winding which comprises a plurality of turns of conductor which are wound around a periphery of a measurement area; and

a second winding which extends substantially over the measurement area and which comprises at least two series connected loops which are arranged in succession along a measurement direction within the measurement area, with each loop comprising a plurality of primary conductors which cross the measurement direction and a plurality of connecting conductors which extend along the measurement direction for connecting the primary conductors to each other; and

wherein at least one of said primary conductors of said second winding is located between the turns of conductor of said first winding.

31. An apparatus according to any of claims 28 to 30, wherein said second winding comprises at least two sets of loops which are arranged in succession along the measurement path and wherein the loops of said at least two sets of loops are arranged so that EMFs induced in loops of the same set by a common background alternating magnetic field add together and so that EMFs induced in the loops of one set by a common background alternating magnetic field oppose the EMFs induced in the loops of the other set.

32. An apparatus according to claim 31, wherein each set of loops comprises the same number of loops.

33. An apparatus according to claim 31 or 32, wherein each set of loops is arranged to enclose substantially the same area.

35. An apparatus according to claim 34, wherein the spacing between the primary conductors of said second winding varies in a sinusoidal manner along said measurement direction.

36. An apparatus according to any of claims 28 to 35, further comprising a third winding which extends substantially over the measurement area and which comprises at least two series connected loops which are arranged in succession along a second different measurement direction within the measurement area, with each loop comprising a plurality of primary conductors which cross the second measurement direction and a plurality of connecting conductors which extend along the second measurement direction for connecting the primary conductors to each other.

37. An apparatus according to claim 36, wherein said second measurement direction is substantially perpendicular to the measurement direction of said second winding.

38. An apparatus according to claim 36 or 37, wherein at least one of the primary conductors of said third winding is located between the turns of conductor of said first winding.

40. An apparatus according to claim 39, wherein said conductor layer comprises a printed circuit board carrying a plurality of conductor tracks on at least one side of the board.

41. An apparatus according to claim 39 or 40, wherein said transducer is suitable for use in a linear position detector.

42. An apparatus according to claim 41, wherein said transducer is suitable for use in a two dimensional linear position detector.

39. A transducer for use in sensing or generating magnetic fields in a position detector, the transducer comprising:

at least one layer of conductor for sensing or for generating magnetic fields; and

a layer of magnetic material located under said at least one layer of conductor for providing a permeable path for magnetic flux to pass behind the conductor layer;

characterised in that said layer of magnetic material comprises spin melt ribbon.

43. An apparatus according to any of claims 39 to 42, wherein said spin melt ribbon layer is between 15 μ

m and 50 μ

m thick.

44. A stylus for use with a position detector, the stylus comprising:

an elongate housing;

a movable tip mounted at one end of the housing for axial movement relative thereto in a first direction from a retracted position to an extended position and in a second, opposite direction from the extended position to the retracted position;

a sensing coil fixed in the housing and having an abutment surface facing in said second direction;

a flux linkage element mounted to the tip for movement relative to the coil; and

movement-limiting means to define the extent of movement of the tip relative to the housing between said extended and retracted positions, said movement-limiting means comprising;

a first limiting element mounted to the flux linkage element and having a first abutment surface facing in said first direction and a second abutment surface facing in said second direction;

a second limiting element fixed in the housing axially adjacent to the coil and having first and second abutment surfaces facing in said first direction, the first abutment surface contacting the abutment surface of the coil; and

the arrangement being such that when the tip is in the retracted position, the second abutment surface of the first limiting element contacts the second abutment surface of the second limiting element and when the tip is in the extended position the second abutment surface of the first limiting element contacts the abutment surface of the coil.

45. A stylus according to claim 44, wherein said flux linkage element is elongate and wherein the first limiting element comprises a blind bore of a predetermined depth for receiving and holding said elongate flux linkage element, whereby when the tip is in said extended position, the end of said elongate element is a predetermined distance from the abutment surface of said coil.

46. A stylus according to claim 44 or 45, wherein said first limiting element slides within a channel of said second limiting element.

47. A stylus according to any of claims 44 to 46, wherein the extent of movement of the tip is defined by the difference between the distance between the first and second abutment surfaces of said second limiting element and the distance between the first and second abutment surfaces of said first limiting element.

49. A stylus according to any of claims 44 to 47, wherein said first and second limiting elements are formed by an injection moulding process.

55. A stylus according to any of claims 44 to 54, wherein said flux linkage element comprises a ferrite rod.

56. A stylus according to any of claims 44 to 55, wherein said coil is a solenoid coil having an axis which is substantially co-axial with the axis of the housing.

57. A stylus according to any of claims 44 to 56, further comprising biasing means for biasing the tip towards said extended position.

58. A stylus according to claim 57, wherein said biasing means comprises spring means which acts against the housing and a said movement limiting means.

59. A stylus according to any of claims 44 to 58, wherein said coil is formed by self bonding wire.

60. A stylus according to any of claims 44 to 59, further comprising a capacitor connected to the ends of said coil, to form a resonant circuit.

61. A stylus according to any of claims 44 to 60, wherein said housing comprises a front portion and a rear portion which fit together by interference fit.

66. A method of detecting the position of first and second members which are relatively moveable along a measurement path, the method comprising the steps of:

providing a winding on one of said first and second members;

providing a stylus according to any of claims 44 to 61 on the other member;

generating a magnetic field with said stylus; and

detecting the generated magnetic field with said winding and detecting therefrom the relative position of said first and second members.

67. A method of detecting the position of first and second members which are relatively moveable along a measurement path, the method comprising the steps of:

providing a winding on one of said first and second members;

providing a stylus according to any of claims 44 to 61 on the other member;

generating a magnetic field with said winding; and

detecting the generated magnetic field with said stylus and detecting therefrom the relative position of said first and second members.

73. A portable data input/output device comprising a stylus according to any of claims 44 to 61.

50. A stylus for use with a position detector, the stylus comprising:

an elongate housing;

a movable tip mounted at one end of the housing for axial movement relative thereto in a first direction from a retracted position to an extended position and in a second, opposite direction from the extended position to the retracted position;

a sensing coil fixed in the housing and having an abutment surface facing in said second direction;

a flux linkage element mounted to the tip for movement relative to the coil; and

movement-limiting means to define the extent of movement of the tip relative to the housing between said extended and retracted positions, said movement-limiting means comprising a limiting element mounted to the flux linkage element and having an abutment surface facing in said first direction for contacting the abutment surface of said coil when the tip is in said extended position;

characterised in that said flux linkage element is elongate and wherein the limiting element comprises a blind bore of a predetermined depth for receiving and holding said elongate element, whereby when the tip is in said extended position, the end of said elongate element is a predetermined distance from the abutment surface of said coil.

51. A stylus for use with a position detector, the stylus comprising:

an elongate housing;

a movable tip mounted at one end of the housing for axial movement between a retracted position and an extended position;

a formerless sensing coil; and

a flux linkage element which extends through the coil;

wherein said formerless coil and said flux linkage element are mounted for relative movement with the movement of said tip, whereby the inductance of said coil is changed with the movement of said tip.

52. A stylus for use with a position detector, the stylus comprising:

an elongate housing;

a movable tip mounted at one end of the housing for axial movement relative thereto in a first direction from a retracted position to an extended position and in a second, opposite direction from the extended position to the retracted position;

a sensing coil;

a flux linkage element;

wherein the sensing coil and the flux linkage element are mounted for relative movement with the movement of said tip, whereby the inductance of said coil is changed with the movement of said tip;

characterised by movement-limiting means which defines the extent of movement of the tip relative to the housing between said extended and retracted positions, said movement-limiting means comprising a first limiting element mounted for movement with the tip and a second movement-limiting element fixed to the housing;

wherein said first and second limiting elements comprise a first abutment surface facing in said first direction and a second abutment surface facing in said second direction and wherein the arrangement is such that when the tip is in the retracted position the second abutment surface of the first limiting element contacts the first abutment surface of the second limiting element and when the tip is in the extended position the first abutment surface of said first limiting element contacts the second abutment surface of said second limiting element.

53. A stylus according to claim 52, wherein said first limiting element comprises an elongate member having a slot and said second limiting member comprises means which slides within said slot.

54. A stylus for use with a position detector, the stylus comprising:

an elongate housing;

a movable tip mounted at one end of the housing for axial movement relative thereto in a first direction from a retracted position to an extended position and in a second, opposite direction from the extended position to the retracted position;

a sensing coil having an abutment surface;

a flux linkage element;

wherein said sensing coil and said flux linkage element are mounted for relative movement with the movement of said tip, whereby the inductance of the coil is changed with the movement of the tip; and

means for limiting the movement of the tip relative to the housing comprising a limiting element mounted for movement with the tip and having an abutment surface facing in said first direction for contacting the abutment surface of said coil when the tip is in said extended position;

characterised in that said flux linkage element is elongate and wherein the limiting element comprises a blind bore of a predetermined depth within said abutment surface for receiving and holding said elongate element, whereby when the tip is in said extended position, the end of said elongate element is a predetermined distance from the abutment surface of said coil.

62. A position sensor comprising:

at least one periodic winding which extends along a measurement path and which has a predetermined pitch; and

a stylus comprising a magnetic field generator having an average magnetic centre which is located approximately 1/(2π

) of the pitch of the periodic winding from a desired apparent measurement point.

63. A sensor according to claim 62, wherein said desired apparent measurement point is approximately the tip of the stylus.