System and method for optical navigation using a projected fringe technique
View Patent ↗A method for determining relative movement between an optical navigation device and a navigation terrain includes generating two overlapping coherent optical beams, and generating a pattern of interference fringes between the two overlapping optical beams. The method further includes illuminating a surface portion of the navigation terrain with the pattern of interference fringes, imaging a fringe-illuminated surface portion, and generating a pattern of signals in response to the imaged fringe-illuminated surface portion.
1. An optical navigation system for determining movement relative to a navigation terrain, said system comprising:
an optical navigation device operable to generate two overlapping beams of coherent optical radiation, said two overlapping beams operable to generate a pattern of interference fringes, such that said two overlapping beams with said fringe pattern are operable to illuminate a surface portion of said navigation terrain;
a detector array operable to generate an output pattern of signals in response to an input optical image pattern; and
an imaging element disposed to image onto said detector array a portion of said navigation terrain surface illuminated with said two overlapping beams.
2. The system of claim 1 further comprising a primary optical source operable to generate a primary beam of coherent optical radiation; and
a beam splitting element operable to split said primary beam of said coherent optical radiation into said two overlapping beams of coherent optical radiation, each of said overlapping beams having substantially the same degree of coherence as said primary beam.
3. The system of claim 2 wherein said primary source is selected from diode emitters, lasers, vertical-cavity surface-emitting lasers (VCSELs), laser diodes, and wavelength tunable light sources.
4. The system of claim 2 wherein said beam splitting element is an optical fiber beam splitter, and said two overlapping beams are diverging beams from two separate but proximate substantial point sources of coherent optical radiation.
5. The system of claim 4 wherein said two separate point sources are disposed to directly illuminate said navigation terrain surface portion.
6. The system of claim 2 wherein said beam splitting element is configured substantially as a Michelson interferometer, and wherein said overlapping beams propagate at an angle relative to one another.
7. The system of claim 6 wherein said Michelson configured interferometer is configured to cause said overlapping beams to illuminate said navigation terrain surface portion.
8. The system of claim 1 wherein said two overlapping beams with said fringe pattern are operable to cause illumination of said navigation terrain surface portion in a pattern of alternating light and dark fringe contours, wherein said contour pattern is a characteristic of modulation of said pattern of interference fringes by topography of said navigation terrain surface portion.
9. The system of claim 1 wherein said imaging element is selected from refractive focusing elements and reflective focusing elements.
10. The system of claim 1 further comprising a processor operable to process said pattern of signals from said detector array and to generate an output representing two-dimensional movement of said navigation terrain portion relative to said interference fringe pattern.
11. The system of claim 10 wherein said processor comprises an algorithm operable to correlate successive frames of signals from said detector array to generate said two-dimensional movement output.
12. The system of claim 1 further comprising two separate sources of coherent optical radiation, each said separate source operable to generate one of said two overlapping beams of coherent optical radiation.
13. The system of claim 12 wherein said two separate sources are operable to be phase locked relative to one another.
14. The system of claim 12 further comprising a diffractive optical element disposed to diffract one of said two overlapping beams of coherent optical radiation.
15. The system of claim 12 wherein said two separate sources are selected from diode emitters, lasers, vertical-cavity surface-emitting lasers (VCSELs), laser diodes, and wavelength tunable light sources.
16. A method for determining relative movement between an optical navigation device and a navigation terrain, said method comprising:
generating two overlapping coherent optical beams;
generating a pattern of interference fringes between said two overlapping optical beams;
illuminating a surface portion of said navigation terrain with said pattern of interference fringes;
imaging a portion of said fringe-illuminated surface; and
generating a pattern of signals in response to said imaged fringe-illuminated surface portion.
17. The method of claim 16 wherein said generating two overlapping coherent optical beams comprises:
generating a primary beam of coherent optical radiation from a single optical source; and
dividing said primary beam into two overlapping coherent optical beams, each of said overlapping optical beams having substantially the same degree of coherence as said primary beam.
18. The method of claim 17 wherein said primary beam is generated by an optical source selected from diode emitters, lasers, vertical-cavity surface-emitting lasers (VCSELs), laser diodes, and wavelength tunable optical sources.
19. The method of claim 17 wherein said dividing is performed using an optical fiber beam splitter, such that said two overlapping beams diverge from two separate but proximate substantial point sources of coherent optical radiation.
20. The method of claim 17 wherein said dividing is performed using substantially a Michelson interferometer, and wherein said overlapping beams propagate at an angle relative to one another.
21. The method of claim 16 additionally comprising processing said pattern of signals to generate an output signal representing two-dimensional movement of said navigation terrain portion relative to said interference fringe pattern.
22. The method of claim 21 further comprising correlating successive frames of said output signals to generate said two-dimensional movement output.
23. The method of claim 21 wherein said output signal controls a positional pointer on the display of a computer.
24. The method of claim 16 wherein said generating two overlapping coherent optical beams comprises generating each of said overlapping coherent optical beams from a separate optical source.
25. The method of claim 24 wherein said separate optical sources are phase locked relative to one another.
26. The method of claim 24 wherein said separate optical sources are selected from diode emitters, lasers, vertical-cavity surface-emitting lasers (VCSELs), laser diodes, and wavelength tunable optical sources.
27. A computer input pointer, said pointer comprising:
means for emitting at least two beams of coherent light incident upon a surface at a non-zero angle to each other;
means for generating an image of an interference pattern on said surface created by said at least two beams;
means for relating said image to a topography of said surface; and
means for determining movement of said pointer relative to said surface by comparing successive images from said image generating means.
28. The pointer of claim 27 wherein said emitting means is a Michelson interferometer.
29. The pointer of claim 27 wherein said image generating means is an array of photo-detectors.
30. The pointer of claim 27 wherein said determining means uses a Moire metrology to detect changes in said topography of said surface.
31. The system of claim 1 wherein each said beam is generated by its own light source.