Digitiser system

• US 20070085836A1
• Filed: 08/26/2004
• Published: 04/19/2007
• Est. Priority Date: 08/26/2003
• Status: Active Grant

• Current Assignee: Synaptics (UK) Ltd. (Synaptics Incorporated)
• Original Assignee: Synaptics (UK) Ltd. (Synaptics Incorporated)
• Inventors: Ely, David
• Granted Patent: US 7,812,268 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

An X-Y digitiser system is described for embedding within a host device, such as a tablet PC, a mobile telephone, a personal digital assistant or the like. The digitiser is configurable so that it can detect and track the position of different types of position indicator. The digitiser that is described also includes novel digitiser windings and novel excitation circuitry for energising the windings.

Claims

1. A digitiser controller comprising:

a memory for storing a plurality of position indicator calibration data, each associated with a respective type of position indicator;

a survey module operable to control the digitiser to survey for the presence, adjacent to a working surface of the digitiser, of the different types of position indicators defined by the stored position indicator calibration data; and

a position sensing module operable to control the digitiser to track the position of any position indicator identified by said survey module as being adjacent to the working surface of the digitiser, in accordance with the stored position indicator calibration data for the identified position indicator.

2. A controller according to claim 1, wherein said survey module is operable to survey for one or more of:

a battery powered position indicator, a single resonator position indicator, a multi-resonator position indicator and a position indicator having a resonator and processing electronics.

3. A controller according to claim 1, wherein said survey module is operable to survey for the different types of position indicator individually.

4. A controller according to claim 3, wherein the survey module is operable to survey for the presence of each different type of position indicator in an order defined by the position indicator calibration data.

5. A controller according to claim 3, wherein said survey module is operable to survey for a position indicator having a resonator and a position indicator having a resonator and processing electronics, and wherein said survey module is operable to survey for the position indicator having a resonator after the position indicator having a resonator and processing electronics.

6. A controller according to claim 1, wherein said position indicator calibration data includes data specifying the survey process to be used by the digitiser for surveying for the associated type of position indicator.

7. A controller according to claim 1, further comprising a capture module operable to control the digitiser to capture the position of any position indicators identified by the survey module as being adjacent to the working surface of the digitiser, in accordance with the stored position indicator calibration data for the or each identified position indicator, and wherein said position sensing module is operable to track the position of any position indicators captured by said capture module.

8. A controller according to claim 1, wherein said position indicator calibration data includes data specifying the position sensing process to be used by the digitiser for tracking the position of the associated type of position indicator.

9. A controller according to claim 1, wherein said digitiser is operable to determine the position of a position indicator using a measurement process for a generic position indicator, wherein said position indicator calibration data includes position indicator specific data and wherein said position sensing module is operable to correct the position measurement obtained from the measurement process for the generic position indicator using the position indicator specific data in the associated position indicator calibration data.

10. A controller according to claim 9, wherein said position indicator calibration data includes data defining the position of an effective magnetic centre of the position indicator and wherein said position sensing module is operable to correct the position measurement obtained from the measurement process for the generic position indicator using the data defining the position of the effective magnetic centre of the position indicator.

11. A controller according to claim 1, wherein said position sensing module is operable to estimate the frequency of a signal emitted by the position indicator.

12. A controller according to claim 11, wherein said position sensing module is operable to use the position indicator calibration data to determine status information for the position indicator using the estimated frequency of said signal.

13. A controller according to claim 1, wherein said position sensing module is operable to estimate the phase of a signal emitted by the position indicator.

14. A controller according to claim 13, wherein said position sensing module is operable to use the position indicator calibration data to determine status information for the position indicator using the estimated phase of said signal.

15. A controller according to claim 1, wherein for a position indicator having a resonator, said survey process is operable to cause said digitiser to energise digitiser windings thereof in order to energise the resonator of said position indicator.

16. A controller according to claim 15, wherein said survey process is operable to cause said digitiser to energise said digitiser windings with excitation signals at different excitation frequencies, in order to energise over a pre-determined frequency band defined by the position indicator calibration data.

17. A controller according to claim 15, wherein said survey module is operable to cause said digitiser to process signals generated in digitiser windings thereof, to estimate the resonant frequency of the resonator.

18. A controller according to claim 17, wherein said position sensing module is operable to use the estimated resonator frequency determined by the survey module, to cause said digitiser to energise digitiser windings thereof with an excitation signal whose frequency is determined in dependence upon the estimated resonator frequency.

19. A controller according to claim 18, wherein said position sensing module is operable to determine an excitation configuration of said digitiser windings which causes power to be efficiently transferred between the digitiser and the position indicator.

20. A controller according to claim 1, comprising a microprocessor and wherein said modules include software modules for controlling the operation of said microprocessor.

21. A controller according to claim 1, wherein said modules are formed by hardware circuits.

22. A digitiser comprising a plurality of digitiser windings arrayed over a working area of the digitiser, a position indicator for indicating positions over said working area of said digitiser and a digitiser controller according to any preceding claim for controlling the digitiser to detect and to track the position indicated by said position indicator over the working area.

23. A digitiser according to claim 22, wherein said position indicator comprises a stylus.

25. A computer readable medium storing processor implementable instructions for configuring a programmable processor as the digitiser controller of claim 1.

26. Processor implementable instructions for configuring a programmable processor as the digitiser controller of claim 1.

24. A method of controlling a digitiser, the method comprising:

controlling the digitiser to survey for the presence, adjacent to a working surface of the digitiser, of different types of position indicators defined by stored position indicator calibration data; and

controlling the digitiser to track the position of any position indicators identified in the survey step as being adjacent to the working surface of the digitiser, in accordance with the stored position indicator calibration data for the or each identified position indicator.

27. An excitation circuit for generating and for applying an excitation signal to selected conductors of a digitiser, the excitation circuit comprising:

an excitation signal generator for generating an excitation signal for application to the selected conductors of the digitiser; and

conductor select switching circuitry operable;

i) to receive the excitation signal generated by the excitation signal generator; and

ii) to apply the excitation signal to the selected digitiser conductors identified by one or more select control signals;

wherein the conductor select switching circuitry includes a plurality of switching circuits each associated with a respective digitiser conductor, each being operable to control the application of said excitation signal to the associated digitiser conductor in dependence upon said one or more select control signals; and

wherein at least one of said switching circuits includes a single transistor switch for controlling the application of the excitation signal to the associated digitiser conductor.

28. An excitation circuit according to claim 27, wherein each of said switching circuits includes a single transistor switch for controlling the application of the excitation signal to the associated digitiser conductor.

29. An excitation circuit according to claim 28, wherein said plurality of switching circuits are arranged in two groups, with the single transistor of each switching circuit in the first group being for connection between a supply potential and the associated digitiser conductor and with the single transistor of each switching circuit in the second group being for connection between a reference potential and the associated digitiser conductor.

30. An excitation circuit according to claim 27, wherein said excitation signal generator comprises a pulse generator operable to receive digital control signals from a digitiser controller and operable to generate a periodic sequence of voltage pulses in dependence upon the received control signals and an inductor-capacitor filter operable for filtering the sequence of voltage pulses to generate said excitation signal.

31. An excitation circuit according to claim 30, wherein said pulse generator is operable to generate said sequence of voltage pulses at an excitation frequency defined by the digital control signals.

32. An excitation circuit according to claim 30, wherein the frequency response of said inductor-capacitor filter is adaptable for different excitation frequencies or for different selected digitiser conductors.

33. An excitation circuit according to claim 32, wherein said inductor-capacitor filter has an adjustable resonant frequency.

34. An excitation circuit according to claim 33, wherein said inductor-capacitor filter includes one or more capacitors and one or more switches for switching said one or more capacitors in and out of circuit with the filter, for varying the resonant frequency of said filter.

35. An excitation circuit according to claim 30, wherein said pulse generator is operable to generate a sequence of double pulses, with the timing between successive double pulse being dependent upon the desired excitation frequency and with the timing between the pulses of each pair being set in order to reduce one or more harmonics of the excitation frequency.

36. An excitation circuit according to claim 30, further comprising said digitiser controller, which is operable to generate digital control signals for varying the duration of each pulse generated by said pulse generator in order to obtain a desired amplitude of excitation current.

37. An excitation circuit according to claim 27, wherein said excitation signal generator further comprises a snubbing circuit for snubbing out the generated excitation signal at the end of an excitation burst.

38. An excitation circuit according to claim 27, wherein when the excitation signal is applied to the selected digitiser windings, a reverse EMF is induced in one or more of the switching circuits associated with the non-selected digitiser windings, and wherein said excitation signal generator is operable to generate an excitation voltage at a level which prevents said reverse EMFs from causing substantial reverse conduction of said switching circuits.

39. An excitation circuit according to claim 27, wherein the or each transistor switch is a MOSFET switch.

40. A digitiser system comprising:

at least one set of digitiser conductors arrayed over a working area, each digitiser conductor extending substantially in a first direction and being spaced apart along a second direction; and

a digitiser controller comprising;

an excitation signal generator for generating an excitation signal for application to selected ones of said digitiser conductors;

conductor select switching circuitry operable;

i) to receive the excitation signal generated by the excitation signal generator; and

ii) to apply the excitation signal to the selected digitiser conductors identified by one or more select control signals; and

a controller operable to generate said one or more select control signals for controlling said conductor select switching circuitry;

wherein said controller is operable, in a first mode, to generate select control signals for causing said conductor select switching circuitry to apply said excitation signal to digitiser conductors which are spaced apart along said second direction by a first spacing and is operable, in a second mode, to generate select control signals for causing said conductor select switching circuitry to apply said excitation signal to digitiser conductors which are spaced apart along said second direction by a second smaller spacing.

41. A system according to claim 40, wherein said digitiser conductors are spaced in a second direction which is substantially orthogonal to said first direction.

42. A system according to claim 40, wherein said digitiser conductors are connected together at or near one end by a connecting conductor and wherein the other end of some or all of said digitiser conductors are for connection to said conductor select switching circuitry.

43. A system according to claim 40, further comprising a movable indicator for moving over said working area and for interacting with said digitiser conductors.

44. A system according to claim 43, wherein said movable indicator is a position indicator.

45. A system according to claim 44, wherein said controller has a survey mode in which the controller is operable to determine initial data relating to said position indicator, and a tracking mode in which the controller is operable to track the position of the position indicator over said working area.

46. A system according to claim 45, wherein said first mode of said controller corresponds to said survey mode.

47. A system according to claim 45, wherein said second mode of said controller corresponds to said tracking mode.

48. A system according to claim 45, wherein said one or more select control signals are for causing said conductor select switching circuitry to apply said excitation signal to digitiser conductors in the vicinity of a previously reported position of said position indicator.

49. A digitiser controller for use in the system of claim 40, comprising:

an excitation signal generator for generating an excitation signal for application to selected ones of said digitiser conductors;

conductor select switching circuitry operable;

i) to receive the excitation signal generated by the excitation signal generator; and

ii) to apply the excitation signal to the selected digitiser conductors identified by one or more select control signals; and

a controller operable to generate said one or more select control signals for controlling said conductor select switching circuitry;

wherein said controller is operable, in a first mode, to generate select control signals for causing said conductor select switching circuitry to apply said excitation signal to digitiser conductors which are spaced apart along said second direction by a first spacing and is operable, in a second mode, to generate select control signals for causing said conductor select switching circuitry to apply said excitation signal to digitiser conductors which are spaced apart along said second direction by a second smaller spacing.

50. A computer readable medium storing computer executable instructions for causing a programmable computer device to become configured as the digitiser controller of claim 49.

51. A digitiser system comprising:

a plurality of sensor conductors arrayed over a working area of the digitiser;

a plurality of excitation conductors arrayed over the working area of the digitiser;

a position indicator which is movable over the working area and which, in use, is electromagnetically coupled with said sensor conductors and said excitation conductors;

an excitation circuit operable to generate an excitation signal for application to a selected one or more of said excitation conductors, for transmitting signals to said position indicator;

a sensing circuit operable to sense signals generated in said sensor conductors as a result of the electromagnetic interaction between the sensor conductors and the position indicator, each sensor signal varying with the respective electromagnetic coupling between the position indicator and the corresponding sensor conductor; and

a digitiser controller comprising;

i) a processing circuit operable to process the sensor signals sensed by said sensing circuit to determine which one or more of said excitation conductors should be selected to receive the excitation signal generated by said excitation circuit;

wherein said processing circuit is operable to determine a coupling measure for each of a plurality of excitation configurations, each excitation configuration corresponding to the selection of a respective one or more of said excitation conductors and each coupling measure being determined from one or more of said sensor signals and being an indication of the electromagnetic coupling between the one or more excitation conductors for that excitation configuration and said position indicator;

wherein said processing circuit is operable to determine a coupling measure for at least one of said excitation configurations as a function of two or more of said sensor signals determined by said sensing circuit; and

ii) a selection circuit operable to process the determined coupling measures for the plurality of excitation configurations to select a current excitation configuration to be used to transmit said signals to said position indicator.

52. A digitiser according to claim 51, wherein one or more of the sensor conductors are also excitation conductors.

53. A digitiser according to claim 51, wherein said sensor conductors and said excitation conductors are arrayed in first and second directions over said working area.

54. A digitiser according to claim 51, wherein, the signals transmitted by said excitation conductors are for energising said position indicator.

55. A digitiser according to claim 51, wherein said processing circuit is operable to determine a measure of the amplitude of the sensor signals and is operable to determine said coupling measure for each excitation configuration in dependence upon the amplitude of one or more of said sensor signals.

56. A digitiser according to claim 55, wherein said processing circuit is operable to determine the coupling measure for an excitation configuration in dependence upon the sensor signals from three or more sensor conductors that are in the vicinity of the excitation conductors for that excitation configuration.

57. A digitiser according to claim 51, wherein said sensing circuit is operable to sense signals generated in sensor coils formed by two or more of said sensor conductors and wherein said processing circuit is operable to determine a coupling measure for one or more of said excitation configurations as a function of the sensor signals sensed by said sensing circuit from two or more of said sensor coils.

58. A digitiser controller for use in the digitiser system of claim 51, the digitiser controller comprising:

a processing circuit operable to process the sensor signals sensed by said sensing circuit to determine which one or more of said excitation conductors should be selected to receive the excitation signal generated by said excitation circuit;

wherein said processing circuit is operable to determine a coupling measure for each of a plurality of excitation configurations, each excitation configuration corresponding to the selection of a respective one or more of said excitation conductors and each coupling measure being determined from one or more of said sensor signals and being an indication of the electromagnetic coupling between the one or more excitation conductors for that excitation configuration and said position indicator;

wherein said processing circuit is operable to determine a coupling measure for at least one of said excitation configurations as a function of two or more of said sensor signals determined by said sensing circuit; and

a selection circuit operable to process the determined coupling measures for the plurality of excitation configurations to select a current excitation configuration to be used to transmit said signals to said position indicator.

59. A set of digitiser windings for use in a digitiser, the set of digitiser windings comprising a plurality of digitiser conductors arrayed over a working area, the digitiser conductors extending substantially in a first direction within the working area and being spaced apart along a second direction within the working area;

and

wherein said set of digitiser windings are arranged so that the density of said digitiser conductors within at least one edge portion of said working area is greater than the density of digitiser conductors within a central portion of said working area.

60. A set of digitiser windings according to claim 59, wherein said plurality of digitiser conductors are spaced apart along a second direction which is substantially orthogonal to said first direction.

61. A set of digitiser windings according to claim 59, wherein each digitiser conductor is connected at or near one end to at least one other digitiser conductor and is connectable at the other end to digitiser electronics.

62. A set of digitiser windings according to claim 61, wherein each digitiser conductor is connected at or near said one end to each other digitiser conductor by a connecting conductor which extends substantially along said second direction.

63. A set of digitiser windings according to claim 59, wherein said plurality of digitiser conductors are substantially parallel.

64. A set of digitiser windings according to claim 59, wherein said plurality of digitiser conductors is a first plurality and further comprising a second plurality of digitiser conductors arrayed over said working area, which second plurality of digitiser conductors extend substantially in said second direction and which are spaced apart along said first direction.

65. A set of digitiser windings according to claim 64, wherein said second plurality of digitiser conductors are arranged so that the density of said second plurality of digitiser conductors is greater at a second edge portion of said working area than the density of said second plurality of digitiser conductors in a central portion of said working area.

66. A set of digitiser windings according to claim 64, wherein respective ones of said second plurality of digitiser conductors are connected together to define an array of conductor loops.

67. A set of digitiser windings according to claim 66, wherein said second plurality of digitiser conductors are connected to form an array of non-overlapping conductor loops.

68. A set of digitiser windings according to claim 66, comprising a set of connecting conductors, each connected at one end to a respective conductor loop and the other end being for connection to digitiser electronics and wherein the plurality of connecting conductors extend along said first direction.

69. A set of digitiser windings according to claim 68, wherein said set of connecting windings are provided between digitiser conductors of said first plurality of digitiser conductors.

70. A set of digitiser windings according to claim 68, wherein at least one of said connecting conductors for connecting said conductor loops to said digitiser electronics is formed by one of said digitiser conductors of said first plurality of digitiser conductors.

71. A set of digitiser windings according to claim 59, wherein one or more of said digitiser conductors are formed as conductor tracks on a printed circuit board.

72. A set of digitiser windings for use in a digitiser, the set of digitiser windings comprising:

a first plurality of digitiser conductors arrayed over a working area, the digitiser conductors of the first plurality extending substantially in a first direction within said working area and being spaced apart along a second direction within said working area, wherein each digitiser conductor of said first plurality is connected at or near one end to the other digitiser conductors of said first plurality by a connecting conductor which extends along said second direction and is connectable at the other end to digitiser electronics;

a second plurality of digitiser conductors arrayed over said working area, said digitiser conductors of said second plurality extending substantially in said second direction and being spaced apart along said first direction;

wherein said second plurality of digitiser conductors are connected together to form a plurality of conductor loops which are arrayed over said working area; and

a plurality of connecting conductors for connecting said array of conductor loops to digitiser electronics, which connecting conductors extend substantially in said first direction.

73. A set of digitiser windings according to claim 72, wherein one or more of said connecting conductors are formed by one or more of said digitiser conductors of said first plurality.

74. A set of digitiser windings according to claim 72, wherein said connecting conductors extend along said first direction between the digitiser conductors of said first plurality.

75. A set of digitiser windings according to claim 72, wherein said second plurality of digitiser conductors are arranged to form an array of non-overlapping conductor loops.

76. A set of digitiser windings according to claim 72, wherein adjacent pairs of conductor loops share a common connecting conductor.

77. A set of digitiser windings according to a claim 72, wherein said digitiser conductors and said connecting conductors are formed as conductors on a printed circuit board.