Method and apparatus for sensing of position

• US 5,239,307 A
• Filed: 01/31/1992
• Issued: 08/24/1993
• Est. Priority Date: 10/10/1989
• Status: Expired due to Term

• Current Assignee: Micro Encoder, Inc. (Mitutoyo Corporation)
• Original Assignee: Micro Encoder, Inc. (Mitutoyo Corporation)
• Inventors: Andermo, Ingvar
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US07/830,543
• Time in Patent Office: 571 Days
• Field of Search: 324/660, 324/661, 324/686, 324/690, 324/207.23, 340/870.37, 340/870.30, 178/87
• US Class Current: 340/870.37
• CPC Class Codes: G01D 5/2412 by varying overlap
• CPC Class Codes: G01D 5/2415 adapted for encoders

Abstract

A method and apparatus for sensing both axial and angular displacements of a collar relative to a shaft. The invention provides transmitting and receiving electrodes on the shaft and coupling electrodes on the collar. Displacements in the axial or angular directions vary the amount of signal conveyed between the electrodes relative to the quantities sought to be measured. An electronic package provides the appropriate signals and allows multiplexing of the data.

Claims

1. A system for measuring the relative position between first and second objects in first and second orthogonal directions, said system comprising:

a plurality of rows of electrodes mounted on said first object, said rows being spaced apart from each other in said second direction with the spacing between each of said rows and any adjacent row being substantially constant, said rows of electrodes and the electrodes in said rows each having an elongated configuration with a longitudinal axis extending in said first direction, each of said row of electrodes containing a first electrode and at least a second electrode of substantially equal length in said first direction, the electrodes in each of said rows being positioned adjacent each other in said second direction, the sum of the dimensions in said second direction of all of the electrodes in each of said rows that are used to measure in said second direction being constant along the length of said row in said first direction, and the dimension in said second direction of said first electrode relative to the dimension in said second direction of said second electrode varying along said first direction;

a coupling electrode mounted on said second object adjacent the electrodes mounted on said first object so that said coupling electrode is spaced apart from said rows of electrodes in a third direction that is orthogonal to said first and second directions, said coupling electrode having a dimension in said second direction that is at least equal to the distance in said second direction between one edge of a row that receives a first electrical signal during a measurement in said second direction and the corresponding edges of a corresponding row that receives a second electrical signal during a measurement in said second direction;

first electronic means operatively connected to said coupling electrode and to the electrodes in said rows of electrodes for comparing a first signal that is a function of the capacitive coupling between at least a portion of said coupling electrode and the adjacent electrodes in at least one of said rows with a second signal that is a function of the capacitive coupling between at least one other said coupling electrode and the adjacent electrodes in at least one other of said rows to measure the relative positions between said first and second objects in said second direction; and

second electronic means operatively connected to said coupling electrode and to the electrodes in said rows of electrodes for comparing a third signal that is a function of the capacitive coupling between at least said first electrode in at least one of said rows of electrodes and said adjacent coupling electrode with a fourth signal that is a function of the capacitive coupling between at least said second electrode in at least one of said rows of electrodes and said adjacent coupling electrode to measure the relative positions between said first and second objects in said first direction.

2. The system of claim 1 wherein the ratio between the dimension of said first electrode and the dimension of said second electrode in said second direction is the same for a plurality of said rows of electrodes at the same position in said first direction, and wherein said second electronic means determines the relative position between said first and second objects in said first direction by applying a first common signal to the first electrode in one row of electrodes and to the first electrode in at least one other row of electrodes, and wherein said second electronic means determines the relative position between said first and second objects in said first direction by applying a second common signal to the second electrode in said one row of electrodes and to the second electrode in said at least one other row of electrodes such that the capacitive coupling between said coupling electrode and the first electrodes in said rows of electrodes is compared to the capacitive coupling between said coupling electrode and the second electrodes in said rows of electrodes.

3. The system of claim 1 wherein said first and second electrodes in each of said rows of electrodes have a triangular configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a linear manner in said first direction, said triangular first and second electrodes being arranged so that together they have a rectangular configuration.

4. The system of claim 1 wherein said first and second electrodes in each of said rows have a periodic configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a periodic manner in said first direction.

5. The system of claim 4 wherein said periodic configuration is sinusoidal so that said capacitive coupling between said coupling electrode and said first and second electrodes to varies in a sinusoidal manner in said first direction.

6. The system of claim 4 wherein the spatial frequency of the electrodes in adjacent first and second rows differ from each other in a predetermined manner, and wherein said second electronic means further includes means for measuring the relative position between said first and second objects in said first direction over a range covering a plurality of cycles of the periodic electrodes in said first and second rows, said measuring means comprising:

first analysis means for comparing the capacitive coupling between said coupling electrode and each of the electrodes in said first row to determine the spatial phase of the periodic electrodes in said first row that are opposite said coupling electrode;

second analysis means for comparing the capacitive coupling between said coupling electrode and each of the electrodes in said second row to determine the spatial phase of the periodic electrodes in said second row that are opposite said coupling electrode;

comparison means for comparing the spatial phase of the periodic electrodes in said first row with the spatial phase of the periodic electrodes in said second row; and

calculating means for determining the relative position between said first and second objects in said first direction from the difference in the spatial phases of the electrodes in said first and second rows and the spatial periods of the periodic electrodes in said first and second rows.

7. The system of claim 5 wherein said rows of electrodes each further includes a third electrode having a sinusoidal configuration, said first, second, and third electrodes being arranged so that they are phased 120 degrees apart from each other and so that together they have a dimension in said second direction that is constant with respect to said first direction.

8. The system of claim 1 wherein said first and second directions are in respective axial and circumferential directions.

9. The system of claim 1 wherein said first object is a cylindrical axle the circumference of which constitutes said second direction and the longitudinal axis of which constitutes said first direction, and wherein said second object is a cylindrical collar surrounding said shaft.

10. The system of claim 1 wherein said second electronic means for measuring the relative position between said first and second objects in said first direction comprise:

first signal generating means for applying a signal to the first electrode in at least one of said rows of electrodes;

first measuring means for determining a property of a first signal derived from a signal coupled to said coupling electrode from the signal applied to said first electrode;

second signal generating means for applying a signal to the second electrode in at least one of said rows of electrodes;

second measuring means for determining the property of a second signal derived from a signal coupled to said coupling electrode from the signal applied to said second electrode; and

comparison means for comparing the property of said first signal to the property of said second signal.

11. The system of claim 1 wherein said second electronic means for measuring the relative position between said first and second objects in said first direction comprise:

signal generating means for applying a signal to said coupling electrode;

first measuring means for determining a property of a first signal derived from a signal coupled to the first electrode of at least one of said rows of electrodes from the signal applied to said coupling electrode;

second measuring means for determining the property of a second signal derived from a signal coupled to at least the second electrode of at least one of said rows of electrodes from the signal applied to said coupling electrode; and

comparison means for comparing the property of said first signal to the property of said second signal.

12. The system of claim 1 wherein said first electronic means comprise:

first signal generating means for applying a signal to all of the electrodes in one row of electrodes;

first measuring means for determining a property of a first signal derived from a signal coupled to said coupling electrode from the signal applied to the electrodes in said one row of electrodes;

second signal generating means for applying a signal to all of the electrodes in at least one other row of electrodes;

second measuring means for determining the property of a second signal derived from a signal coupled to said coupling electrode from the signal applied to the electrodes in said other row of electrodes; and

first comparison means for comparing the property of said first signal to the property of said second signal.

13. The system of claim 1 wherein said first electronic means further includes means for measuring the relative position between said first and second objects in said second direction in two scales, said means comprising:

first signal generating means for applying a signal to all of the electrodes in a first plurality of rows that are positioned adjacent each other to effectively provide a first row of electrodes having a relatively large dimension in said second direction;

second signal generating means for applying a signal to all of the electrodes in a second plurality of rows that are positioned adjacent each other to effectively provide a second row of electrodes having a relatively large dimension in said second direction;

first measuring means for determining a property of a first signal derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said first row of electrodes;

second measuring means for determining the property of a second signal derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said second row of electrodes;

first comparison means for comparing the property of said first signal to the property of said second signal to determine the relative position between said first and second objects in said second direction in a relatively coarse scale;

third signal generating means for applying a signal to all of the electrodes in a first number of adjacent rows, the number of rows to which said signal is applied being at least equal to 1 but less than the number of rows in said first plurality of rows to effectively provide a third row of electrodes having a relatively small dimension in said second direction;

fourth signal generating means for applying a signal to all of the electrodes in a second number of adjacent rows, the number of rows to which said signal is applied being at least equal to 1 but less than the number of rows in said second plurality of rows to effectively provide a fourth row having a relatively small dimension in said second direction;

third measuring means for determining a property of a third signal derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said third row of electrodes;

fourth measuring means for determining the property of a fourth signal derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said fourth row of electrodes; and

second comparison means for comparing the property of said third signal to the property of said fourth signal to determine the relative position between said first and second objects in said second direction in a relatively fine scale.

14. The system of claim 13 wherein said signal generating means comprise:

an oscillator generating a periodic signal;

a multiplexer selectively coupling said periodic signal to said electrodes in response to a control signal; and

a processor operatively connected to said multiplexer, said processor generating said control signal to selectively apply said periodic signal to predetermined combinations of said electrodes.

15. The system of claim 14 wherein said multiplexer additionally selectively couples and uncouples portions of said coupling electrode in response to a control signal, and said processor additionally generates said control signal to selectively connect and disconnect predetermined combinations of portions of said coupling electrode.

16. The system of claim 1 wherein said first electronic means for measuring the relative position between said first and second objects in said second direction comprises:

signal generating means for applying a signal to said coupling electrode;

first measuring means for determining a property of a first signal derived from a signal coupled to all of the electrodes in at least one row of electrodes from the signal applied to said coupling electrode;

second measuring means for determining the property of a second signal derived from a signal coupled to all of the electrodes in at least one other row of electrodes from the signal applied to said coupling electrodes; and

comparison means for comparing the property of said first signal to the property of said second signal.

17. The system of claim 1 said first electronic means further includes means for measuring the relative position between said first and second objects in said second direction in two scales, said means comprising:

first comparison means for comparing the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a first plurality of rows that are positioned adjacent each other with the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a second plurality of rows that are positioned adjacent each other to measure the relative positions between said first and second objects in said second direction in a relatively coarse scale; and

second comparison means for comparing the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a first number of adjacent rows with the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a second number of adjacent rows, said first and second number of rows being at least equal to 1 but less than the number of rows in said first and second plurality of rows, respectively, thereby measuring the relative positions between said first and second objects in said second direction in a relatively fine scale.

18. The system of claim 1, further including at least one pickup electrode mounted on said first object so that it is adjacent but spaced apart from said coupling electrode in a third direction that is orthogonal to said first and second directions, and wherein said electronic means needs no direct connection to said coupling electrode and further includes means for measuring the magnitude of a signal derived from a signal applied to the electrodes in said row of electrodes and coupled from the electrodes in said row of electrodes to said coupling electrode, and from said coupling electrode to said pickup electrode.

19. The system of claim 1 wherein said coupling electrode is divided into a plurality of subelectrodes positioned adjacent each other in said second direction, each of said subelectrodes having a dimension in said second direction that at least as large as the dimension of said rows in said second direction.

20. The system of claim 19 wherein the sum of the dimensions in said first direction of all of said coupling subelectrodes that are used to measure in said first direction is constant along said second direction.

21. The system of claim 19 wherein said subelectrodes are adjacently placed at a minimum spacing in said second direction which is sufficient to maintain electrical isolation.

22. The system of claim 19 wherein said coupling subelectrodes have a dimension in said second direction which is substantially equal to the distance between corresponding edges of said rows of electrodes in said second direction and all of said rows are of substantially equal dimension in said second direction.

23. The system of claim 19 wherein said first electronic means includes means for comparing the capacitive coupling between at least one subelectrode of said coupling electrode and all of the electrodes in at least two of said rows with the capacitive coupling between at least one other subelectrode of said coupling electrode and all of the electrodes in at least two of said rows.

24. The system of claim 1 wherein said coupling electrode has a periodic configuration so that the capacitive coupling between said coupling electrode and all of the electrodes in said row varies in a periodic manner when said objects move relative to each other in said second direction.

25. The system of claim 1 wherein corresponding electrodes in a first set of said rows are interconnected with each other, and wherein corresponding electrodes in a second set of rows are interconnected with each other, the rows in said first set alternating with the rows in said second set.

26. The system of claim 25 wherein said coupling electrode is divided into a plurality of subelectrodes having respective periodic configurations with differing spatial phases and a common spatial period corresponding to the distance in said second direction between an electrode edge in one set and the adjacent corresponding electrode edge in the same set, and wherein said first electronic means for measuring the relative position between said first and second objects in said second direction includes means for comparing a signal that is a function of the capacitive coupling between selected subelectrodes of said coupling electrode and all of the adjacent electrodes in said first and second sets of rows with a signal that is a function of the capacitive coupling between selected other subelectrodes of said coupling electrode and all of the adjacent electrodes in said first and second sets of rows.

27. The system of claim 1 wherein said coupling electrode has a dimension in said second direction that is substantially equal to an integer multiple "N," N greater than or equal to 1, times the distance in said second direction between one edge of a row that receives a first electrical signal during measurement in said second direction and the corresponding edge of a corresponding row that receives a second electrical signal during measurement in said second direction.

28. The system of claim 1 wherein the dimension in said first direction of said coupling electrode is constant along said second direction.

29. The system of claim 1, further comprising:

dividing said coupling electrode into at least two subelectrodes, each having substantially the same dimension in said second direction that is substantially equal to an integer multiple "N," N greater than or equal to 1, of the distance in said second direction between one edge of a row that receives a first electrical signal during measurement in said second direction and the corresponding edge of a corresponding row that receives a second electrical signal during measurement in said second direction;

wherein said first electronic means is operatively connected to at least one coupling subelectrode for comparing said first signal, that is a function of the capacitive coupling between at least one subelectrode of said coupling electrode and the adjacent electrodes in at least one of said rows, with said second signal that is a function of the capacitive coupling between at least one operatively connected subelectrode of said coupling electrode and the adjacent electrodes in at least one other of said rows, to measure the relative positions between said first and second objects in said second direction; and

wherein said second electronic means is operatively connected to at least one coupling subelectrode for comparing said third signal, that is a function of the capacitive coupling between said first electrode in at least one of said rows of electrodes and at least one adjacent coupling subelectrode, with said fourth signal that is a function of the capacitive coupling between at least said second electrode in at least one of said rows of electrodes and at least one adjacent coupling subelectrode, to measure the relative positions between said first and second objects in said first direction.

30. A method of measuring the relative position between first and second objects in first and second orthogonal directions, said method comprising:

mounting a plurality of rows of electrodes on said first object, said rows being spaced apart from each other in said second direction with the spacing between each of said rows and any adjacent row being substantially constant, said rows and the electrodes in each of said rows having an elongated configuration with a longitudinal axis extending in said first direction, each of said rows of electrodes containing a first electrode and at least a second electrode of substantially equal length in said first direction, the electrodes in each of said rows being positioned adjacent each other in said second direction, the sum of the dimensions in said second direction of all of the electrodes in each of said rows that are used to measure in said second direction being constant along the length of said row in said first direction, and the dimension in said second direction of said first electrode relative to the dimension in said second direction of said second electrode varying along said first direction;

mounting a coupling electrode on said second object adjacent said rows of electrodes so that it is spaced apart from said rows of electrodes in a third direction that is orthogonal to said first and second directions, said coupling electrode having a dimension in said second direction that is at least equal to the distance in said second direction between one edge of a row that receives a first electrical signal during a measurement in said second direction and the corresponding edge of a corresponding row that receives a second electrical signal during a measurement in said second direction;

comparing the capacitive coupling between said coupling electrode and the adjacent electrodes in at least one of said rows with the capacitive coupling between said coupling electrode and the adjacent electrodes in at least one other of said rows to measure the relative positions between said first and second objects in said second direction; and

comparing the capacitive coupling between said first electrode in at least one of said rows of electrodes and said adjacent coupling electrode with the capacitive coupling between said second electrode in at least one of said rows of electrodes and said adjacent coupling electrode to measure the relative positions between said first and second objects in said first direction.

31. The method of claim 30 wherein said coupling electrode has a dimension in said second direction which is substantially equal to the distance between corresponding edges of said rows of electrodes in said second direction.

32. The method of claim 30 wherein the capacitive coupling between said first electrode in at least one of said rows of electrodes and said adjacent coupling electrode is compared with the capacitive coupling between all electrodes in that same row of electrodes and said adjacent coupling electrode to measure the relative positions between said first and second objects in said first direction.

33. The method of claim 30 wherein the ratio between the dimension of said first electrode and the dimension of said second electrode in said second direction is the same for a plurality of said rows of electrodes at the same position in said first direction, and wherein the relative position between said first and second objects in said first direction is measured with the first electrode in one row of electrodes connected to the first electrode in at least one other row of electrodes, and the second electrode in said one row of electrodes connected to the second electrodes in said other row of electrodes such that said first signal is a function of the capacitive coupling between said coupling electrode and the first electrodes in a plurality of said rows of electrodes, and said second signal is a function of the capacitive coupling between said coupling electrode and the second electrodes in a plurality of said rows of electrodes.

34. The method of claim 30 wherein said first and second electrodes in each of said rows of electrodes have a triangular configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a linear manner in said first direction, and wherein the triangular first and second electrodes are arranged so that together they have a rectangular configuration.

35. The method of claim 30 wherein said first and second electrodes in each of said rows have a periodic configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a periodic manner in said first direction.

36. The method of claim 35 wherein said periodic configuration causes said capacitive coupling between said coupling electrode and said first and second electrodes to vary in a sinusoidal manner in said first direction.

37. The method of claim 35 wherein the spatial frequency of the electrodes in adjacent first and second rows differ from each other in a predetermined manner, and wherein the relative position between said first and second objects is measured in said first direction over a range covering a plurality of cycles of the periodic electrodes in said first and second rows by the steps of:

determining the spatial phase of the periodic electrodes opposite the coupling electrode in said first row by comparing the capacitive coupling between said coupling electrode and each of the electrodes in said first row;

determining the spatial phase of the periodic electrodes opposite the coupling electrode in said second row by comparing the capacitive coupling between said coupling electrode and each of the electrodes in said second row;

comparing the spatial phase of the periodic electrodes in said first row with the spatial phase of the periodic electrodes in said second row; and

determining the relative position between said first and second objects in said first direction within said range from the difference in the spatial phases of the electrodes in first and second rows and the spatial periods of the periodic electrodes in said first and second rows.

38. The method of claim 37 wherein said spatial frequency in said first row is a higher frequency than in said second row, and wherein after said relative position determination in said first direction to define position with relatively coarse resolution, the capacitive coupling between said coupling electrode and said first electrode in said first row is compared with the capacitive coupling between said coupling electrode and at least said second electrode in said first row to measure the relative positions between said first and second objects to a relative finer resolution and accuracy and combining the coarse and fine resolution measurements to measure position unambiguously and absolutely in said first direction.

39. The method of claim 36 wherein said rows of electrodes each further includes a third electrode having a sinusoidal configuration, said first, second, and third electrodes being arranged so that they are phased 120 degrees apart from each other and so that together they have a dimension in said second direction that is constant with respect to said first direction.

40. The method of claim 30 wherein said first and second directions are in respective axial and circumferential directions.

41. The method of claim 30 wherein the relative position between said first and second objects in said first direction is measured by the steps of:

applying a signal to the first electrode in at least one of said rows of electrodes;

obtaining a first signal that is derived from a signal coupled to said coupling electrode from the signal applied to said first electrode;

applying a signal to at least the second electrode in at least one of said rows of electrodes;

obtaining a second signal that is derived from a signal coupled to said coupling electrode from the signal applied to at least said second electrode; and

comparing a property of said first signal to a property of said second signal.

42. The method of claim 41 wherein said property is the magnitude of the voltages of said first and second signals.

43. The method of claim 41 wherein said property is the magnitude of the phases of said first and second signals.

44. The method of claim 30 wherein the relative position between said first and second objects in said first direction is measured by the steps of:

applying a signal to said coupling electrode;

obtaining a first signal that is derived from a signal coupled to said first electrode from the signal applied to said coupling electrode;

obtaining a second signal that is derived from a signal coupled to the second electrode in at least one of said rows of electrodes from the signal applied to said coupling electrode; and

comparing a property of said first signal to a property of said second signal.

45. The method of claim 30 wherein the relative position between said first and second objects in said second direction is measured by the steps of:

applying a signal to all of the electrodes in one row of electrodes;

obtaining a first signal that is derived from a signal coupled to said coupling electrode from the signal applied to the electrodes in said one row of electrodes;

applying a signal to all of the electrodes in another row of electrodes;

obtaining a second signal that is derived from a signal coupled to said coupling electrode from the signal applied to the electrodes in said other row of electrodes; and

comparing a property of said first signal to a property of said second signal.

46. The method of claim 45 wherein the relative position between said first and second objects in said second direction is measured in two scales by the steps of:

applying a signal to all of the electrodes in a first plurality of rows that are positioned adjacent each other to effectively provide a first row of electrodes having a relatively large dimension in said second direction;

obtaining a first signal that is derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said first row of electrodes;

applying a signal to all of the electrodes in a second plurality of rows that are positioned adjacent each other to effectively provide a second row of electrodes having a relatively large dimension in said second direction;

obtaining a second signal that is derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said second row of electrodes;

determining the relative position between said first and second objects in said second direction in a relatively coarse scale by comparing a property of said first signal to a property of said second signal;

applying a signal to all of the electrodes in a first number of adjacent rows, the number of rows to which said signal is applied being at least equal to one but less than the number of rows in said first plurality of rows to effectively provide a third row of electrodes having a relatively small dimension in said second direction;

applying a signal to all of the electrodes in a second number of adjacent rows, the number of rows to which said signal is applied being at least equal to one but less than the number of rows in said second plurality of rows to effectively provide a fourth row having a relatively small dimension in said second direction;

obtaining a third signal that is derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said third row of electrodes;

obtaining a fourth signal that is derived from a signal coupled to at least a portion of said coupling electrode from the signal applied to the electrodes in said fourth row of electrodes; and

determining the relative position between said first and second objects in said second direction in a relatively fine scale by comparing a property of said third signal to a property of said fourth signal.

47. The method of claim 46 wherein said third and fourth rows are of equal width and adjacently placed and said third row of electrodes is adjacently repeated alternately with said fourth row of electrodes at least once and connected to form a set considered to be the said third electrode and said fourth row of electrodes is adjacently repeated alternately with said third row of electrodes at least once and connected to form a set considered to be said fourth electrode.

48. The method of claim 47 wherein said coupling electrode is divided into at least two subelectrodes which have a periodic configuration so that the capacitive coupling between said subelectrodes and said rows varies in a periodic manner when moving in said second direction.

49. The method of claim 48 wherein said periodic configuration is sinusoidal with a spatial period substantially equal to the spatial period of the electrode rows within the set comprising said third or fourth electrode.

50. The method of claim 30 wherein the relative position between said first and second objects in said second direction is measured by the steps of:

applying a signal to said coupling electrode;

obtaining a first signal that is derived from a signal coupled to all of the electrodes in one row of electrodes from the signal applied to said coupling electrode;

obtaining a second signal that is derived from a signal coupled to all of the electrodes in another row of electrodes from the signal applied to said coupling electrodes; and

comparing a property of said first signal to a property of said second signal.

51. The method of claim 30 wherein the relative position between said first and second objects in said second direction is measured in two scales by the steps of:

comparing the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a first plurality of rows that are positioned adjacent each other with the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a second plurality of rows that are positioned adjacent each other to measure the relative positions between said first and second objects in said second direction in a relatively coarse scale; and

comparing the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a first number of adjacent rows with the capacitive coupling between at least a portion of said coupling electrode and all of the electrodes in a second number of adjacent rows, said first and second number of rows being at least equal to one but less than the number of rows in said first and second plurality of rows, respectively, thereby measuring the relative positions between said first and second objects in said second direction in a relatively fine scale.

52. The method of claim 30 wherein said steps of comparing the capacitive coupling includes the steps of:

applying signals to at least one of the electrodes in said rows of electrodes;

mounting at least one pickup electrode on said first object so that it is adjacent but spaced apart from said coupling electrode in a third direction that is orthogonal to said first and second directions; and

detecting a signal on said pickup electrode resulting from the signal applied to at least one of the electrodes in said rows of electrodes being coupled from the electrodes in said row of electrodes to said coupling electrode, and from said coupling electrode to said pickup electrode.

53. The method of claim 30 wherein said coupling electrode is divided into a plurality of subelectrodes mounted on said second object, each of said coupling subelectrodes having a dimension in said second direction selected so that each of said coupling subelectrodes cannot completely overlay more than one of said rows.

54. The method of claim 53 wherein the sum of the dimensions in said first direction of all of said coupling subelectrodes that are used to measure in said first direction is constant along said second direction.

55. The method of claim 53 wherein said subelectrodes are adjacently placed at a minimum spacing in said second direction which is sufficient to maintain electrical isolation.

56. The method of claim 30 wherein said coupling electrode is divided into a plurality of subelectrodes positioned adjacent each other in said second direction, each of said subelectrodes having a dimension in said second direction that is at least as large as the dimension of said rows in said second direction, and wherein the relative position between said first and second objects is measured in said second direction by the steps of comparing the capacitive coupling between at least one subelectrode of said coupling electrode and its adjacent rows with the capacitive coupling between at least one other subelectrode of said coupling electrode and its adjacent rows.

57. The method of claim 56 wherein said coupling subelectrodes have a dimension in said second direction which is substantially equal to the distance between corresponding edges of said rows of electrodes in said second direction and all of said rows are of substantially equal dimension in said second direction.

58. The method of claim 30 wherein said coupling electrode has a periodic configuration so that the capacitive coupling between said coupling electrode and all of the electrodes in said row varies in a periodic manner when said objects move relative to each other in said second direction.

59. The method of claim 58 wherein the coupling between said coupling electrode and the electrodes in said rows is determined by the step of comparing the capacitive coupling between said coupling electrode and a first set of said rows with the capacitive coupling between said coupling electrode and a second set of said rows, the rows in said first set alternating with the rows in said second set, when measuring in said second direction.

60. The method of claim 59 wherein said coupling electrode is divided into a plurality of subelectrodes having respective periodic configurations with differing spatial phases and a common spatial period corresponding to the distance in said second direction between an electrode edge in one set and the adjacent corresponding electrode edge in the same set, and wherein the relative position between said first and second objects in said second direction is measured by the step of comparing the capacitive coupling between selected subelectrodes of said coupling electrode and all of the electrodes in said first and second sets of rows with the capacitive coupling between selected other subelectrodes of said coupling electrode and all of the electrodes in said first and second sets of rows.

61. The method of claim 30 wherein said coupling electrode has a dimension in said second direction that is substantially equal to an integer multiple "N," N greater than or equal to 1, time the distance in said second direction between one edge of a row that receives a first electrical signal during measurement in said second direction and the corresponding edge of a corresponding row that receives a second electrical signal during measurement in said second direction.

62. The method of claim 30 wherein the dimension in said first direction of said coupling electrode is constant along said second direction.

63. The method of claim 30, further comprising:

dividing said coupling electrode into at least two subelectrodes, each having substantially the same dimension in said second direction that is substantially equal to an integer multiple "N," N greater than or equal to 1, of the distance in said second direction between one edge of a row that receives a first electrical signal during measurement in said second direction and the corresponding edge of a corresponding row that receives a second electrical signal during measurement in said second direction;

wherein the capacitive coupling between at least one subelectrode of said coupling electrode and the adjacent electrodes in at least one of said rows is compared with the capacitive coupling between at least one subelectrode of said coupling electrode and the adjacent electrodes in at least one other of said rows to measure the relative positions between said first and second objects in said second direction; and

wherein the capacitive coupling between said first electrode in at least one of said rows of electrodes and at least one adjacent coupling subelectrode is compared with the capacitive coupling between at least said second electrode in at least one of said rows of electrodes and at least one adjacent coupling subelectrode, to measure the relative positions between said first and second objects in said first direction.

64. A method of measuring the relative position between first and second objects in a first direction, said method comprising:

mounting at least one row of electrodes on said first object, said row containing a first electrode and at least a second electrode of substantially equal length in said first direction, said row of electrodes and the electrodes in said row having an elongated configuration with a longitudinal axis extending in said first direction, the dimension in a second direction of said first electrode relative to the dimension in said second direction of said second electrode varying along said first direction said second direction being orthogonal to said first direction;

mounting a coupling electrode on said second object adjacent said row of electrodes so that it is spaced apart from said row of electrodes in a third direction that is orthogonal to said first and second directions; and

comparing the capacitive coupling between said coupling electrode and said first electrode in said row with the capacitive coupling between said coupling electrode and said second electrode in said row, thereby measuring the relative positions between said first and second objects in said first direction.

65. The method of claim 64 wherein said first and second electrodes have a triangular configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a linear manner in said first direction.

66. The method of claim 64 wherein said first and second electrodes have a periodic configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a periodic manner in said first direction.

67. The method of claim 66 wherein first and second rows of electrodes are mounted on said first object with said rows of electrodes and the electrodes in said rows of electrodes being positioned adjacent each other in said second direction, wherein the spatial frequency of the electrodes in adjacent first and second rows differ from each other in a predetermined manner, and wherein the relative position between said first and second objects is measured in said first direction over a range covering a plurality of cycles of the periodic electrodes in said first and second rows by the steps of:

determining the spatial phase of the periodic electrodes in said first row that are opposite said coupling electrode by comparing the capacitive coupling between said coupling electrode and each of the electrodes in said first row;

determining the spatial phase of the periodic electrodes in said second row that are opposite said coupling electrode by comparing the capacitive coupling between said coupling electrode and each of the electrodes in said second row;

comparing the spatial phase of the periodic electrodes in said first row with the spatial phase of the periodic electrodes in said second row; and

determining the relative position between said first and second objects in said first direction within said range from the difference in the spatial phases of the electrodes in first and second rows and the spatial periods of the periodic electrodes in said first and second rows.

68. The method of claim 64 wherein the relative position between said first and second objects in said first direction is measured by the steps of:

applying a signal to said first electrode;

applying a signal to said second electrode;

obtaining a first signal derived from a signal coupled to said coupling electrode from the signal applied to said first electrode;

obtaining a second signal derived from a signal coupled to said coupling electrode from the signal applied to said second electrode; and

comparing a property of said first signal to a property of said second signal.

69. The method of claim 64 wherein the relative position between said first and second objects in said first direction is measured by the steps of:

applying a signal to said coupling electrode;

obtaining a first signal derived from a signal coupled to said first electrode from the signal applied to said coupling electrode;

obtaining a second signal derived from a signal coupled to said second electrode from the signal applied to said coupling electrode; and

comparing a property of said first signal to a property of said second signal.

70. The method of claim 64 wherein said step of comparing the capacitive coupling includes the steps of:

applying signals to said first and second electrodes;

mounting at least one pickup electrode on said first object so that it is adjacent but spaced apart from said coupling electrode in a third direction that is orthogonal to said first direction; and

detecting a signal on said pickup electrode resulting from the signal applied to said first and second electrodes being coupled from said first and second electrodes to said coupling electrode, and from said coupling electrode to said pickup electrode.

71. A system for measuring the relative position between first and second objects in a first direction, said system comprising:

at least one row of electrodes mounted on said first object, said row containing a first electrode and at least a second electrode of substantially equal length in said first direction, said row and the electrodes in said row having an elongated configuration with a longitudinal axis extending in said first direction, the dimension in a second direction of said first electrode relative to the dimension in said second direction of said second electrode varying along said first direction, said second direction being orthogonal to said first direction;

a coupling electrode mounted on said second object adjacent said row of electrodes so that said coupling electrode is spaced apart from said row of electrodes in a third direction that is orthogonal to said first and second directions; and

electronic means for comparing a first signal that is a function of the capacitive coupling between said coupling electrode and said first electrode in said row with a second signal that is a function of the capacitive coupling between said coupling electrode and said second electrode in said row, thereby measuring the relative positions between said first and second objects in said first direction.

72. The system of claim 71 wherein said first and second electrodes have a triangular configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a linear manner in said first direction.

73. The system of claim 71 wherein said first and second electrodes have a periodic configuration so that the capacitive coupling between said coupling electrode and said first and second electrodes varies in a periodic manner in said first direction.

74. The system of claim 73 wherein first and second rows of electrodes are mounted on said first object with said rows of electrodes and the electrodes in said rows of electrodes being positioned adjacent each other in a second direction orthogonal to said first direction, the spatial frequency of the electrodes in adjacent first and second rows differing from each other in a predetermined manner.

75. The system of claim 74 wherein said electronic means further includes means for measuring the relative position between said first and second objects in said first direction over a range covering a plurality of cycles of the periodic electrodes in said first and second rows, said means comprising:

first measuring means for determining the spatial phase of the periodic electrodes in said first row by comparing a plurality of signals that are functions of the respective capacitive coupling between said coupling electrode and each of the electrodes in said first row;

second measuring means for determining the spatial phase of the periodic electrodes in said second row by comparing a plurality of signals that are functions of the respective capacitive coupling between said coupling electrode and each of the electrodes in said second row;

comparison means for comparing the spatial phase of the periodic electrodes in said first row with the spatial phase of the periodic electrodes in said second row; and

analysis means for determining the relative position between said first and second objects in said first direction within said range from the difference in the spatial phases of the electrodes in first and second rows and the spatial periods of the periodic electrodes in said first and second rows.

76. The system of claim 75 wherein said spatial frequency in said first row is a higher frequency that in said second row, and wherein said analysis means makes said relative position determination in said first direction to define position with relatively coarse resolution over a relatively long range, and corrects and augments said coarse position information with the spatial phase information from said first measuring means to determine position to a relatively finer resolution and accuracy and determine position unambiguously and absolutely in said first direction.

77. The system of claim 71 wherein said electronic means comprises:

first signal generating means for applying a signal to said first electrode;

second signal generating means for applying a signal to said second electrode;

first measuring means for determining a property of a first signal derived from a signal coupled to said coupling electrode from the signal applied to said first electrode;

second measuring means for determining a property of a second signal derived from a signal coupled to said coupling electrode from the signal applied to said second electrode; and

comparison means for comparing the property of said first signal to the property of said second signal.

78. The system of claim 71 wherein said electronic means comprise:

signal generating means for applying a signal to said coupling electrode;

first measuring means for determining a property of a first signal derived from a signal coupled to said first electrode from the signal applied to said coupling electrode;

second measuring means for determining the property of a second signal derived from a signal coupled to said second electrode from the signal applied to said coupling electrode; and

comparison means for comparing the property of said first signal to the property of said second signal.

79. The system of claim 71, further including a pickup electrode mounted on said first object so that it is adjacent but spaced apart from said coupling electrode in a third direction that is orthogonal to said first direction, and wherein said electronic means needs no connection to said coupling electrode and further includes means for comparing a first signal derived from a signal applied to said first electrode and coupled from said first electrode to said coupling electrode, and from said coupling electrode to said pickup electrode, with a second signal derived from a signal applied to said second electrode and coupled from said second electrode to said coupling electrode and to said pickup electrode.

80. A method of measuring the relative position between first and second objects in a first direction, said method comprising:

mounting a plurality of electrodes on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

mounting a coupling electrode having a periodic configuration on said second object adjacent the electrodes mounted on said first object so that said coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction, said coupling electrode having a dimension in said first direction that is at least equal to the distance between one edge of an electrode that receives a first electrical signal during a measurement in said first direction and the corresponding edge of a corresponding electrode that receives a second electrical signal during a measurement in said first direction; and

comparing the capacitive coupling between said coupling electrode and at least one of said electrodes with the capacitive coupling between said coupling electrode and at least one other of said electrodes, the capacitive coupling between said coupling electrode and said electrode varying in a periodic manner when said objects move relative to each other in said first direction, thereby measuring the relative positions between said first and second objects in said first direction.

81. A method of measuring the relative position between first and second objects in a first direction, said method comprising:

mounting a plurality of electrodes on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

mounting a coupling electrode on said second object adjacent the electrodes mounted on said first object so that said coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction, said coupling electrode having a dimension in said first direction that is substantially equal to an integer multiple "N," N greater than or equal to 1, times the distance in said first direction between one edge of a row that receives a first electrical signal during measurement in said first direction and the corresponding edge of a corresponding row that receives a second electrical signal during measurement in said first direction; and

comparing the capacitive coupling between said coupling electrode and at least one of said electrodes with the capacitive coupling between said coupling electrode and at least one other of said electrodes, thereby measuring the relative positions between said first and second objects in said first direction.

82. A method of measuring the relative position between first and second objects in a first direction, said method comprising:

mounting a plurality of electrodes on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

mounting a coupling electrode on said second object adjacent the electrodes mounted on said first object so that said coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction, said coupling electrode having a dimension in said first direction that is at least equal to the distance between one edge of an electrode that receives a first electrical signal during a measurement in said first direction and the corresponding edge of a corresponding electrode that receives a second electrical signal during a measurement in said first direction; and

comparing the capacitive coupling between said coupling electrode and at least one of said electrodes with the capacitive coupling between said coupling electrode and at least one other of said electrodes by the steps of;

applying signals to said electrodes;

mounting at least one pickup electrode on said first object so that it is spaced apart from said coupling electrode in a third direction that is orthogonal to said first direction; and

detecting a signal on said pickup electrode resulting from the signal applied to said electrodes being coupled from said electrodes to said coupling electrode, and from said coupling electrode to said pickup electrode, thereby measuring the relative positions between said first and second objects in said first direction.

83. A method of measuring the relative position between first and second objects in a first direction, said method comprising:

mounting a plurality of electrodes on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

mounting a coupling electrode on said second object adjacent the electrodes mounted on said first object so that said coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction;

dividing said coupling electrode into at least two subelectrodes, each having substantially the same dimension in said first direction that is substantially equal to an integer multiple "N," N greater than or equal to 1, of the distance in said first direction between one edge of a row that receives a first electrical signal during measurement in said first direction and the corresponding edge of a corresponding row that receives a second electrical signal during measurement in said first direction; and

comparing the capacitive coupling between at least one subelectrode of said coupling electrode and the adjacent electrodes in at least one of said rows with the capacitive coupling between at least one subelectrode of said coupling electrode and the adjacent electrodes in at least one other of said rows to measure the relative positions between said first and second objects in said first direction.

84. A method of measuring the relative position between first and second objects in a first direction, said method comprising:

mounting a plurality of electrodes on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

mounting a coupling electrode on said second object adjacent the electrodes mounted on said first object so that said coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction, said coupling electrode having a dimension in said first direction that is at least equal to the distance between one edge of an electrode that receives a first electrical signal during a measurement in said first direction and the corresponding edge of a corresponding electrode that receives a second electrical signal during a measurement in said first direction, each of said coupling electrodes being divided into a plurality of subelectrodes positioned adjacent each other in said first direction; and

comparing the capacitive coupling between at least one subelectrode of said coupling electrode and adjacent electrodes on said first object with the capacitive coupling between at least one other subelectrode of said coupling electrode and adjacent electrodes on said first object, thereby measuring the relative positions between said first and second objects in said first direction.

85. The method of claim 84 wherein the sum of the dimensions in said second direction of all of said coupling subelectrodes that are used to measure in said first direction is constant along said first direction.

86. The method of claim 84 wherein said subelectrodes are adjacently placed at a minimum spacing in said first direction which is sufficient to maintain electrical isolation.

87. A system for measuring the relative position between first and second objects in a first direction, said system comprising:

a plurality of electrodes mounted on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

a coupling electrode mounted on said second object adjacent the electrodes mounted on said first object so that coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction, said coupling electrode being divided into a plurality of subelectrodes positioned adjacent each other in said first direction, each of said subelectrodes having a dimension in said first direction that at least as large as the dimension of said electrodes in said first direction; and

electronic means for comparing a signal that is a function of the capacitive coupling between at least one subelectrode of said coupling electrode and adjacent electrodes on said first object with a signal that is a function of the capacitive coupling between at least one other subelectrode of said coupling electrode and adjacent electrodes on said first object, thereby measuring the relative positions between said first and second objects in said first direction.

88. A system for measuring the relative position between first and second objects in a first direction, said system comprising:

a plurality of electrodes mounted on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

a coupling electrode mounted on said second object adjacent the electrodes mounted on said first object so that coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction, said coupling electrode having a dimension in said first direction that is at least equal to the distance between one edge of an electrode that receives a first electrical signal during a measurement in said first direction and the corresponding edge of a corresponding electrode that receives a second electrical signal during a measurement in said second direction;

a pickup electrode mounted on said first object so that it is spaced apart from said coupling electrode in a third direction that is orthogonal to said first direction and said second direction; and

electronic means for comparing a first signal that is a function of the capacitive coupling between said coupling electrode and at least one of said electrodes with a second signal that is a function of the capacitive coupling between said coupling electrode and at least one other of said electrodes, said capacitive coupling being measured by measuring the magnitude of a signal derived from a signal applied to said electrodes, and coupled from said electrodes to said coupling electrode, and from said coupling electrode to said pickup electrode, thereby measuring the relative positions between said first and second objects in said first direction.

89. A system for measuring the relative position between first and second objects in a first direction, said system comprising:

a plurality of electrodes mounted on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

a coupling electrode mounted on said second object adjacent the electrodes mounted on said first object so that coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction,

said coupling electrode being divided into at least two subelectrodes, each having substantially the same dimension in said first direction that is substantially equal to an integer multiple "N", N greater than or equal to 1, of the distance in said first direction between one edge of a row that receives a first electrical signal during measurement in said first direction and the corresponding edge of a corresponding row that receives a second electrical signal during measurement in said first direction; and

wherein said first signal is a function of the capacitive coupling between at least one subelectrode of said coupling electrode and the adjacent said electrode and said second signal is a function of the capacitive coupling between at least one subelectrode and the adjacent said at least one other electrode, thereby measuring the relative positions between said first and second objects in said first direction.

90. A system for measuring the relative position between first and second objects in a first direction, said system comprising:

a plurality of electrodes mounted on said first object so that said electrodes are positioned adjacent each other in said first direction with the spacing between each of said electrodes and any adjacent electrode being substantially constant, the dimensions in said first direction of each of said electrodes being constant along the length of said electrodes in a second direction orthogonal to said first direction;

a coupling electrode mounted on said second object adjacent the electrodes mounted on said first object so that coupling electrode is spaced apart from said electrodes in a third direction that is orthogonal to said first direction and said second direction, said coupling electrode having a dimension in said first direction that is substantially equal to an integer multiple "N," N greater than or equal to 1, times the distance in said first direction between one edge of a row that receives a first electrical signal during measurement in said first direction and the corresponding edges of a corresponding row that receives a second electrical signal during measurement in said first direction; and

electronic means for comparing a first signal that is a function of the capacitive coupling between said coupling electrode and at least one of said electrodes with a second signal that is a function of the capacitive coupling between said coupling electrode and at least one other of said electrodes, thereby measuring the relative positions between said first and second objects in said first direction.