Optical translation measurement

• US 6,424,407 B1
• Filed: 09/07/2000
• Issued: 07/23/2002
• Est. Priority Date: 03/09/1998
• Status: Expired due to Term

• Current Assignee: OTM Technologies Ltd.
• Original Assignee: OTM Technologies Ltd.
• Inventors: Kinrot, Uri, Kinrot, Opher, Lederer, Gilad
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/623,652
• Time in Patent Office: 684 Days
• Field of Search: 356/399, 356/400, 356/28, 356/285, 356/505, 356/493, 345/166
• US Class Current: 356/28
• CPC Class Codes: G01D 5/347 using displacement encoding scales
• CPC Class Codes: G01P 3/366 by using diffraction of light for measuring speed of fluids G01P5/26
• CPC Class Codes: G01P 3/806 in devices of the type to be classified in G01P3/68
• CPC Class Codes: G01S 17/50 Systems of measurement based on relative movement of target
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G06F 3/0312 for tracking the rotation of a spherical or circular member, e.g. optical rotary encoders used in mice or trackballs using a tracking ball or in mouse scroll wheels tracking relative movement in co-operation with a regularly or irregularly patterned surface, e.g. as in optical mice G06F3/0317; constructional details of scroll or thumb-wheels G06F3/0362; optical rotary encoders G01D5/3473

Abstract

A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident illumination; detecting illumination reflected from the surface to form at least one detected signal; and determining the amount of relative motion parallel to the surface from said at least one detected signal, characterized in that said determining includes correcting for the effects of relative motion perpendicular to the surface.

Claims

1. A method for determining the relative motion of a surface with respect to a measurement device comprising:

illuminating the surface with incident illumination;

detecting a first portion of said incident illumination reflected from the surface in a first direction to form a first detected signal, the time variation of said first signal being responsive to the relative motion in a first direction, said first direction having at least a component in the direction perpendicular to the surface;

detecting a second portion of said incident illumination reflected from the surface in a second direction, different from the first direction, to form a second detected signal the time variation of said second signal being responsive to the relative motion in a second direction, different from the first direction, said second direction having a component in a direction parallel to the surface and in a direction perpendicular to the surface; and

determining the amount of relative motion parallel to the surface free of effects of motion perpendicular to the surface from said first and second detected signals.

2. A method according to claim 1 wherein determining comprises:

generating a third signal from the first and second signals, said third signal being free of the effects of the motion perpendicular to the surface; and

determining the motion parallel to the surface from the third signal.

3. A method according to claim 1 wherein determining comprises:

determining first motion in first direction from the first signal;

determining second motion in the second direction from the second signal; and

determining motion parallel to the surface by correcting the determined second motion by the determined first motion.

4. A method according to claim 1 wherein the first direction does not have a component parallel to the surface.

5. A method according to claim 1, wherein the first direction has a component parallel to the surface.

6. A method according to claim 1 wherein relative motion perpendicular to the surface is determined based on a Doppler shift of the reflected illumination.

7. A method according to claim 1 wherein determining comprises determining the amount of relative motion parallel to the surface directly from the two signals without determining the amount of relative motion perpendicular to the surface.

8. A method according to claim 7 wherein said first detected signal is substantially determined by relative motion perpendicular to the surface.

9. A method according to claim 7 wherein said first detected signal is responsive to relative motion parallel to the surface.

10. A method according to claim 1 and including determining the amount of relative motion perpendicular to the surface.

11. A method according to claim 1 wherein determining the amount of relative motion parallel to the surface includes determining the amount of relative motion along;

two non-colinear directions.

12. A method according to claim 1 wherein the illumination is perpendicularly incident on the surface.

13. A method according to claim 1 wherein detecting comprises coherently detecting.

14. A method according to claim 13 and including:

reflecting or diffracting a portion of the illumination from an object, which is part of the measurement device, to act as a local oscillator.

15. A method according to claim 14 wherein the object is a partially reflecting object through which either the incident or reflected illumination passes.

16. A method according to claim 15 wherein both the incident and reflected illumination pass through the object.

17. A method according to claim 14 wherein the object is adjacent to the surface.

18. A method according to claim 14 wherein the object is a grating.

19. A method according to claim 18 wherein the surface is in the near field of the object.

20. A method according to claim 18 wherein the surface is outside the near field of the grating.

21. A method according to claim 18 wherein the grating produces essentially only a single order of transmitted illumination that illuminates the surface.

22. A method according to claim 14 wherein the illumination is at least partially coherent and wherein the object is placed within the coherence length of the illumination from the surface.

23. A method according to claim 14 wherein the local oscillator illumination and the reflected illumination are incident on at least one detector to produce said signals and wherein the local oscillator illumination and the reflected illumination are at least partly coherent at the detector.

24. A method according to claim 1 wherein the surface is a diffusely reflecting surface and wherein the detected illumination reflected form the surface is diffusely reflected therefrom.

25. Apparatus for measuring relative motion between the apparatus and a surface comprising:

an illumination source, which transmits illumination to illuminate the surface;

a first detector which receives illumination from the source after its reflection from the surface;

an object which reflects a portion of the illumination from the illumination source to said first detector, such that the first detector generates a first signal based on coherent detection of the illumination reflected from the surface with the illumination, that is reflected by the object, functioning as a local oscillator;

a second detector which receives illumination from one of the object and the surface without receiving illumination from the other of the surface and the object and generates a second signal responsive thereto;

a signal corrector that adjusts the first signal for changes in the intensity of the illumination, based on the second signal; and

a motion calculator that calculates the relative motion responsive to the signal from the signal corrector.

26. Apparatus according to claim 25 wherein the illumination of the second detector is illumination from the source reflected from or diffracted by the object.

27. Apparatus according to claim 26 wherein the apparatus includes:

a third detector that receives illumination reflected from the surface without receiving substantial illumination from the object or from the source and produces a third signal in response thereto, and wherein

the signal corrector corrects the adjusted signal based on the third signal.

28. Apparatus according to claim 25 wherein the illumination of the second detector is illumination reflected from the surface.

29. Apparatus according to claim 25 wherein the signal corrector corrects the first signal for a constant term based on the second signal.

30. Apparatus according to claim 29 wherein the signal corrector includes a difference amplifier that receives the first signal and subtracts the second signal from it to produce an adjusted first signal.

31. Apparatus according to claim 30 wherein the signal corrector includes a normalizer that receives the adjusted first signal and normalizes it with respect to the second signal.

32. Apparatus according to claim 25 wherein the object is partially transmitting and wherein the object is placed between the illumination source and the surface such that illumination of the surface passes through the object.

33. Apparatus according to claim 32 wherein the illumination has coherence length and wherein the object and the surface as situated within said coherence length.

34. Apparatus according to claim 25 wherein the object is a grating.

35. Apparatus according to claim 34 wherein the grating produces essentially only a single order of transmitted illumination that illuminates the surface.

36. Apparatus according to claim 34 wherein the surface is within the near field of the grating.

37. Apparatus according to claim 34 wherein the surface is outside the near field of the grating.

38. Apparatus according to claim 25 wherein the illumination reflected from the surface and the illumination reflected by the object are at least partly coherent at the first detector.

39. Apparatus according to claim 25 wherein at least one of the first and second detectors are situated to receive illumination diffusely reflected from the surface.

40. A method for determining the relative motion of an optically diffuse surface with respect to a measurement device comprising:

illuminating the surface with incident illumination from a laser source, such that illumination is reflected from portions of the surface;

diffracting part of the illumination utilizing a grating, which is part of the measurement device, to form reference illumination;

coherently detecting the illumination reflected from the surface utilizing the reference illumination as a local oscillator to form a signal; and

determining the quantity of relative motion of the surface parallel to the grating from the signal.

41. A method according to claim 40 wherein the detected illumination has a coherence length and wherein the grating is placed adjacent to the surface such that the spacing between the grating and the surface is smaller than coherence length.

42. A method according to claim 40 including determining the quantity of relative motion of the surface perpendicular to the grating.

43. A method according to claim 40 wherein determining the quantity of relative motion of the surface parallel to the grating comprises determining the quantity of the motion free from effect of motion perpendicular to the grating.

44. A method according to claim 40 including determining the quantity of motion of the surface in two dimensions.

45. A method according to claim 40 including determining the quantity of motion of the surface in three dimensions.

46. A method according to claim 40 including determining the sense of the direction of motion of the surface.

47. A method according to claim 40 wherein the detection comprises quadrature detection.

48. A method according to claim 40 wherein determining the quantity of relative motion is based on a Doppler shift of the reflected illumination.

49. A method according to claim 40 and including polarizing the illumination reflected from the surface.

50. A method according to claim 40 and wherein the grating produces essentially only a single order of transmitted illumination that illuminates the surface.

51. A method according to claim 40 wherein the incident illumination is linearly polarized.

52. A method for determining the relative motion of a surface with respect to a measurement device comprising:

illuminating the surface with linearly polarized incident illumination from a laser source, such that illumination is reflected from portions of the surface;

polarizing the reflected illumination;

coherently detecting the reflected illumination from the surface utilizing reference illumination derived from the laser source as a local oscillator to form at least two signals;

determining the quantity of relative motion of the surface utilizing the at least two signals.

53. A method according to claim 52 including determining the relative motion parallel to the surface.

54. A method according to claim 52 including determining the quantity of relative motion of the surface in two non-collinear directions.

55. A method according to claim 52 including determining the quantity of relative motion of the surface in three orthogonal directions.

56. A method according to claim 52 including determining the sense of the direction of motion of the surface.

57. A method to claim 52 wherein the detection comprises quadrature detection.

58. A method according to claim 52 wherein determining the quantity of relative motion comprises determining the quantity of relative motion based on a Doppler shift of the reflected illumination.

59. A method according to claim 52 wherein the surface is a diffusely reflecting surface and wherein the detected illumination reflected from the surface is diffusely reflected therefrom.

60. Apparatus for measuring motion relative to a surface, comprising:

at least one laser that illuminates the surface;

at least one object that reflects or diffracts a portion of the illumination to at least three directions in space to act as local oscillator illuminations;

at least three detectors each of which coherently detects illumination reflected from the surface utilizing the local oscillator beams to form at least three signals responsive to the motion of the apparatus relative to the surface; and

circuitry that determines the motion of the apparatus with respect to the surface from the signals,

wherein the at least three detectors comprise at least three detector pairs and wherein the at least three signals comprise at least quadrature-pair signals.

61. Apparatus according to claim 60 including introducing a phase shift between polarization components of the illumination reflected from the surface and polarization components of the local oscillator beams to form the at least three quadrature-pair signals.

62. Apparatus according to claim 60 wherein the motion is determined in two non-colinear directions free from effects of motion in a direction orthogonal to the two directions.

63. Apparatus according to claim 60 at least of the first and second detectors are situated to receive illumination diffusely reflected from the surface.

64. Apparatus according to claim 60 wherein the detected illumination has a coherence length and wherein the object is placed adjacent to the surface such that the spacing between the object and the surface is smaller than the coherence length.

65. Apparatus according to claim 60 wherein the object is a grating.

66. Apparatus for measuring motion relative to a surface, comprising:

at least one laser than illuminates the surface;

at least one object that reflects or diffracts a portion of the illumination to at least three directions in space to act as local oscillator illuminations;

at least three detectors each of which coherently detects illumination reflected from the surface utilizing the local oscillator beams to form at least three responsive to the motion of the apparatus relative to the surface;

circuitry that determines the motion of the apparatus with respect to the surface from the signals; and

a polarizer that polarizes the illumination reflected from the surface.