Precision measuring gauges with optical fiber output channels

• US 20050224705A1
• Filed: 07/29/2004
• Published: 10/13/2005
• Est. Priority Date: 04/09/2004
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Tobiason, Joseph D., Atherton, Kim W., Harsila, Scott, Zwilling, Avron, Emtman, Casey, Goldsworthy, Mike
• Granted Patent: US 7,211,782 B2
• Time in Patent Office: Days
• US Class Current: 250/231.100
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G02B 6/381 of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres

Abstract

All-optical output precision measuring gauges that sense the displacement of an internal scale grating are disclosed. Each type of gauge includes a compact, miniature, or ultra-miniature optical readhead that includes a light source for transmitting light to the scale grating, and optical-fiber detector channels for receiving light from the scale grating and outputting optical measuring signals from the gauge. In various embodiments, the optical-fiber detector channels have respective phase grating masks for receiving a periodic light pattern that moves in correspondence to the scale grating, and the channels are arranged in balanced pairs. In various embodiments, the optical readhead is an interferometric-type optical readhead that provides a measuring resolution as fine as 10-50 nanometers or less. In various embodiments, the gauge is provided in an unprecedented miniature size. In various embodiments, the gauge is motorized to provide a precision actuator.

Claims

1. A precision fiber-optic gauge that senses displacement of a scale grating and outputs all-optical displacement measuring signals, the gauge comprising:

a first member;

a scale grating coupled to a second member that is movable along a measuring axis relative to the first member; and

a fiber-optic readhead coupled to the first member and arranged in an operable position relative to the scale grating, the readhead transmitting light to the scale grating, the readhead comprising at least two fiber-optic detector channels for receiving and spatially filtering light from the scale grating to sense the displacement of the scale grating and outputting all-optical measuring signals based on the received light;

wherein the gauge outputs all-optical measuring signals.

2. The gauge of claim 1, wherein the gauge is selected from a group consisting of a lever gauge, linear gauge, a micrometer, a micrometer head, and rotary stage.

3. The gauge of claim 1, wherein the fiber-optic readhead is of a type selected from a group consisting of a self-imaging type readhead, an imaging type readhead, an absolute type readhead, a two-dimensional type readhead, and an interferometric type readhead.

4. The gauge of claim 1, wherein the readhead comprises multiple fiber-optic detector channels having respective phase grating masks for receiving a periodic light pattern that moves in correspondence to the scale grating so as to detect the location of the scale grating.

5. The gauge of claim 4, wherein the multiple fiber-optic detector channels are arranged in balanced pairs.

6. The gauge of claim 5, wherein three balanced pairs of fiber-optic detector channels are provided.

7. The gauge of claim 4, wherein the readhead comprises an interferometric type fiber-optic readhead, and the scale grating comprises a phase grating such that the periodic light pattern that moves in correspondence to the scale grating is an interferometric light pattern.

8. The gauge of claim 7, wherein at least one outside dimension of the gauge is less than or equal to at least one of 20, 15, 10, or 7 millimeters.

9. The gauge of claim 8, wherein the dimension comprises a height or a thickness of the gauge.

10. The gauge of claim 7, wherein the gauge provides a measuring resolution less than or equal to one of 100, 50, 20, and 10 nanometers.

11. The gauge of claim 4, wherein the readhead comprises a self-imaging type fiber-optic readhead, and the periodic light pattern that moves in correspondence to the scale grating is a self-image light pattern.

12. The gauge of claim 4, wherein the readhead comprises an imaging type fiber-optic readhead, and the periodic light pattern that moves in correspondence to the scale grating is an image light pattern.

13. The gauge of claim 1, wherein the readhead comprises an absolute type fiber-optic readhead or an absolute portion of a fiber-optic readhead that provides output signals usable to provide absolute type measurement values.

14. The gauge of claim 13, wherein the scale grating comprises multiple periodic scale gratings having different periods, and the position of at least one of the scale gratings is detected using the absolute type fiber-optic readhead or absolute portion of the fiber-optic readhead that detects an interferometric light pattern to produce absolute type measurement values.

15. The gauge of claim 13, wherein the scale grating comprises an absolute scale pattern.

16. The gauge of claim 1, wherein the readhead comprises a two-dimensional type fiber-optic readhead that provides output signals usable to provide measurement values along at least two measurement axes.

17. The gauge of claim 1, wherein the gauge is of contact type.

18. The gauge of claim 1, further comprising a light deflecting element provided to deflect a light path of the fiber-optic readhead between the readhead and the scale grating.

19. The gauge of claim 1, further comprising a remote interface box comprising at least one electronic light source and an array of photodetectors that interface with the fiber-optic precision measuring gauge.

20. The gauge of claim 19, wherein the remote interface box outputs electrical signals comprising quadrature signals.

21. The gauge of claim 20, wherein the quadrature signals are sinusoidal analog signals.

22. The gauge of claim 1, which provides a measuring resolution less than or equal to one of 50, 20, and 10 nanometers.

23. The gauge of claim 1, wherein at least one outside dimension of the gauge is less than or equal to 20, 15, 10, or 7 millimeters.

24. The gauge of claim 23, wherein the dimension comprises a height or a thickness of the gauge.

25. The gauge of claim 1 forming a micrometer or a micrometer head.

26. The gauge of claim 25, wherein the micrometer or micrometer head comprises a spindle shaft that carries the linear scale grating.

27. The gauge of claim 26, wherein the spindle shaft defines a groove for receiving the linear scale grating therein.

28. The gauge of claim 25, wherein the micrometer or micrometer head comprises an interferometric-type fiber-optic readhead.

29. The gauge of claim 25, wherein the scale grating has a pitch that is at most 5 microns.

30. The gauge of claim 25, wherein the micrometer or micrometer head provides a measuring resolution less than or equal to at least one of 100, 50, 20, and 10 nanometers.

31. The gauge of claim 25, wherein the micrometer or micrometer head comprises a motor so as to be usable as a precision actuator.

32. The gauge of claim 31, wherein the motorized micrometer or micrometer head comprises an absolute type fiber-optic readhead or an absolute portion of a fiber-optic readhead that provides output signals usable to provide absolute type measurement values based on an absolute linear scale.

33. The gauge of claim 32, wherein the motorized micrometer or micrometer head further comprises a periodic rotary scale and a complementary fiber-optic readhead, and the absolute type measurement values are combined with measurement values derived from the periodic rotary scale to provide a submicron absolute positioning measurement signal.

34. The gauge of claim 1 forming a rotary stage, wherein the scale grating comprises at least a portion of a circular or cylindrical scale grating.

35. The gauge of claim 34, wherein the rotary stage has a nominal diameter that is less than 75, 50, or 30 millimeters.

36. The gauge of claim 34, wherein the rotary stage has a thickness dimension that is less than 30, 20, or 15 millimeters.

37. The gauge of claim 34, wherein the rotary stage provides a measuring resolution less than or equal to one of 5, 2, or 1 arc seconds.

38. The gauge of claim 34, wherein the rotary stage comprises an interferometric-type fiber-optic readhead.

39. The gauge of claim 34, wherein the rotary stage comprises a motor so as to be usable as a precision actuator.

40. The gauge of claim 39, wherein the motorized rotary stage comprises an absolute type fiber-optic readhead or an absolute portion of a fiber-optic readhead that provides output signals usable to provide absolute type measurement values based on an absolute rotary scale.

41. The gauge of claim 40, wherein the motorized rotary stage further comprises a periodic rotary scale and a complementary fiber-optic readhead, and the absolute type measurement values are combined with measurement values derived from the periodic rotary scale to provide a submicron absolute positioning measurement signal.

42. The gauge of claim 1 forming a lever gauge.

43. The gauge of claim 42, wherein the lever gauge has at least one of a height and width dimension that is less than at least one of 20, 15, 10, 7 and 4 millimeters.

44. The gauge of claim 43, wherein both the height and width dimensions of the lever gauge are less than at least one of 20, 15, 10, and 7 millimeters.

45. The gauge of claim 42, which provides a measuring resolution less than or equal to at least one of 50, 20, or 10 nanometers.

46. The gauge of claim 42, wherein the lever gauge comprises an interferometric-type fiber-optic readhead.

47. The gauge of claim 1 forming a linear gauge.

48. The gauge of claim 47, wherein the linear gauge has at least one of a maximum height, maximum width, and nominal barrel diameter dimension that is less than at least one of 10, 7.5, and 5.0 millimeters.

49. The gauge of claim 47, which provides a measuring resolution less than or equal to one of 50, 20, or 10 nanometers.

50. The gauge of claim 47, wherein the linear gauge comprises an interferometric-type fiber-optic readhead.

51. The gauge of claim 1, wherein the gauge is a scanning probe.

52. The gauge of claim 51, wherein the scanning probe provides a measuring resolution less than or equal to one of 50, 20, or 10 nanometers.

53. The gauge of claim 51, wherein the scanning probe comprises an interferometric-type fiber-optic readhead.

54. The gauge of claim 1, wherein the first member comprises a housing that defines a hole, and the gauge further comprises a rotationally alignable member to be received in the hole, the rotationally alignable member being coupled to the readhead and capable of being rotationally aligned with respect to the hole about an axis that is nominally perpendicular to the surface of a phase grating that is part of the fiber-optic readhead and being locked in place in relation to the hole at a desired alignment.

55. The gauge of claim 54, wherein the locking is accomplished by at least one of a clamp, a set screw, and an adhesive.

56. The gauge of claim 54, wherein the rotationally alignable member comprises an element that mates with a corresponding element defined in the hole, such that the mating of the two elements defines the desired alignment.

57. The gauge of claim 56, wherein the element comprises a groove defined in the rotationally alignable member and the corresponding element defined in the hole comprises a keying feature that mates with the groove.

58. The gauge of claim 56, wherein the corresponding element defined in the hole comprises linear features aligned parallel to the axis of the hole that are usable to align the element of the rotationally alignable member precisely parallel to the axis of the hole.

59. The gauge of claim 56, wherein the mating of the two elements further defines the nominal gap of the readhead relative to the scale grating internal to the gauge.

60. The gauge of claim 1, wherein the fiber-optic readhead comprises a light source.

61. The gauge of claim 1, further comprising a standard fiber-optic connector including the fiber-optic readhead.

62. A method for operating a precision fiber-optic gauge that senses displacement of a scale grating and outputs all-optical displacement measuring signals, the gauge comprising:

a first member;

a scale grating coupled to a second member that is movable along a measuring axis relative to the first member; and

a fiber-optic readhead coupled to the first member and arranged in an operable position relative to the scale grating, the readhead transmitting light to the scale grating, the readhead comprising at least two fiber-optic detector channels for receiving and spatially filtering light from the scale grating to sense the displacement of the scale grating and outputting all-optical measuring signals based on the received light;

the method comprising;

(a) operably positioning the fiber-optic readhead relative to the scale grating; and

(b) inputting light arising from the scale grating to the fiber-optic readhead; and

(c) producing all-optical measuring signals from the fiber-optic readhead.

63. The method of claim 62, wherein the first member comprises a housing that defines a hole, and the gauge further comprises a rotationally alignable member to be received in the hole, the rotationally alignable member being coupled to the readhead, and step (a) comprising:

(i) rotationally aligning the rotationally alignable member about an axis that is nominally perpendicular to the surface of a phase grating that is part of the fiber-optic readhead; and

(ii) locking the rotationally alignable member in place in relation to the hole at a desired alignment.

64. The method of claim 63, wherein step (a) further comprises axially aligning the rotationally alignable member to define a nominal gap between the readhead and the scale grating.