Scanning Laser Time of Flight 3D Imaging

• US 20130107000A1
• Filed: 10/27/2011
• Published: 05/02/2013
• Est. Priority Date: 10/27/2011
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Xue, Bin, Jackson, Robert James, Miller, Joshua O., Holmes, Steve, Brown, Margaret K.
• Granted Patent: US 9,684,075 B2
• Time in Patent Office: Days
• US Class Current: 348/46
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4861 Circuits for detection, sampling, integration or read-out
• CPC Class Codes: G01S 7/4865 Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak peak detection in noise, signal conditioning G01S7/487
• CPC Class Codes: G01S 7/4868 Controlling received signal intensity or exposure of sensor

Abstract

Laser light pulses are reflected off a scanning mirror. A time-of-flight distance measurement device receives reflected light pulses and determines distances. The light pulses have abrupt changes in amplitude. Reflected pulses are differentiated to reduce sensitivity to amplitude variations. Differentiated pulses may be compressed to keep the receiver from saturating. Distance measurements are combined with location information to produce a 3D image of a surface.

Claims

1. An apparatus comprising:

a laser light source;

a pulse shaping circuit to drive the laser light source with pulses having an abrupt change in amplitude;

a photodetector to detect reflected light pulses;

a differentiator coupled to the photodetector to differentiate detected pulses;

a compression circuit to compress output signals from the differentiator;

an amplifier to receive compressed signals from the compression circuit and to generate differential output signals;

a detection circuit to detect when the differential output signals cross each other; and

an integrator responsive to the detection circuit for time measurement.

2. The apparatus of claim 1 wherein the pulse shaping circuit is configured to create triangle shaped pulses.

3. The apparatus of claim 1 further comprising at least one scanning mirror to reflect and scan light from the laser light source.

4. The apparatus of claim 3 wherein the laser light source produces light in the nonvisible spectrum.

5. The apparatus of claim 4 wherein the laser light source produces infrared light.

6. The apparatus of claim 4 further comprising at least one laser light source to produce light in the visible spectrum.

7. The apparatus of claim 6 further comprising image processing circuitry to modulate the at least one visible laser light source to display an image while measuring distance at multiple points in a field of view.

8. The apparatus of claim 1 further comprising a second photodetector coupled in a reference signal path to compensate for timing variations.

9. An apparatus comprising:

a laser light source;

a pulse shaping circuit to drive the laser light source with pulses having an abrupt change in amplitude;

a photodetector to detect reflected light pulses;

a differentiator coupled to the photodetector to differentiate detected pulses;

an amplifier to receive signals from the differentiator and to generate differential output signals;

a detection circuit to detect when the differential output signals cross each other;

a power control circuit to modify signal gain at an input to the laser light source in response to a first light pulse train; and

an integrator responsive to the detection circuit for time measurement to integrate over a second light pulse train for time measurement.

10. The apparatus of claim 9 further comprising at least one scanning mirror to reflect and scan light from the laser light source.

11. The apparatus of claim 10 wherein the laser light source produces light in the nonvisible spectrum.

12. The apparatus of claim 11 wherein the laser light source produces infrared light.

13. The apparatus of claim 11 further comprising at least one laser light source to produce light in the visible spectrum.

14. The apparatus of claim 13 further comprising image processing circuitry to drive the at least one laser light source to produce light in the visible spectrum to display an image with visible light while performing distance measurements with nonvisible light.

15. A mobile device comprising:

a scanning laser projector having at least one visible laser light source and a scanning mirror; and

a time of flight distance measurement device that includes a nonvisible laser light source to illuminate the scanning mirror with laser light pulses, and that includes a receive signal path that differentiates and compresses signals representing reflected laser light pulses.

16. The mobile device of claim 15 wherein the mobile device further comprises a wireless interface.

17. The mobile device of claim 15 wherein the time of flight distance measurement device further includes an amplifier to receive compressed signals and to generate differential output signals.

18. The mobile device of claim 17 wherein the time of flight distance measurement device further includes a detection circuit to detect when the differential output signals cross each other.

19. The mobile device of claim 18 wherein the time of flight distance measurement device further includes an integrator responsive to the detection circuit for time measurement.

20. The mobile device of claim 15 wherein the scanning mirror is configured to scan in two dimensions.

22. The mobile device of claim 15 wherein the mobile device further comprises a wireless interface.

23. The mobile device of claim 15 wherein the time of flight distance measurement device further includes an amplifier to receive differentiated signals and to generate differential output signals.

24. The mobile device of claim 23 wherein the time of flight distance measurement device further includes a detection circuit to detect when the differential output signals cross each other.

25. The mobile device of claim 24 wherein the time of flight distance measurement device further includes an integrator responsive to the detection circuit for time measurement.

26. The mobile device of claim 22 wherein the scanning mirror is configured to scan in two dimensions.

21. A mobile device comprising:

a scanning laser projector having at least one visible laser light source and a scanning mirror; and

a time of flight distance measurement device that includes a nonvisible laser light source to illuminate the scanning mirror with laser light pulses, and that includes a receive signal path that differentiates signals representing reflected laser light pulses, and a power control circuit responsive to the receive signal path;

wherein the power control circuit modifies a power level of a second train of light pulses in response to reflections from a first train of light pulses.

27. A 3D imaging device comprising:

a scanning mirror to scan laser light pulses in at least one dimension;

a time of flight distance measurement device to determine distances traveled by reflected laser light pulses; and

at least one motion sensing device coupled to the time of flight distance measurement circuit to increase spatial resolution of collected 3D image data.

28. The 3D imaging device of claim 27 wherein the at least one motion sensing device comprises an accelerometer.

29. The 3D imaging device of claim 27 wherein the at least one motion sensing device comprises a gyroscope.

30. The 3D imaging device of claim 27 wherein the scanning mirror is configured to scan in two dimensions.

31. The 3D imaging device of claim 27 wherein the time of flight distance measurement device comprises a receive path that includes a photodetector, a differentiator, and a compression circuit to compress output from the differentiator.

32. The 3D imaging device of claim 27 further comprising a visible laser light source to produce the laser light pulses.

33. The 3D imaging device of claim 27 further comprising a nonvisible laser light source to produce the laser light pulses.

34. The 3D imaging device of claim 27 further comprising a power control circuit to control laser light pulse power in response to reflected laser light pulses.

35. A 3D imaging device comprising:

a scanning mirror to scan laser light pulses in at least one dimension; and

a time of flight distance measurement device to determine distances traveled by laser light pulses reflected off the scanning mirror.

36. The 3D imaging device of claim 35 wherein the scanning mirror scans the laser light pulses in two dimensions.

37. The 3D imaging device of claim 35 further comprising a second scanning mirror to scan the laser light pulses in a second dimension.

38. The 3D imaging device of claim 35 further comprising a nonvisible laser light source to produce the laser light pulses.

39. The 3D imaging device of claim 38 further comprising at least one visible laser light source to produce visible laser light to be reflected by the scanning mirror.

40. The 3D imaging device of claim 39 further comprising image processing circuitry to drive the at least one visible laser light source to produce light in the visible spectrum to display an image with visible light while performing distance measurements with nonvisible light.

41. A method comprising:

determining distances to an object at a plurality of points during a first horizontal sweep of a scanning laser projector;

recording the distances and the points during the first horizontal sweep as 3D image data;

record panning movement of the scanning laser projector;

determining distances to an object at a plurality of points during a second horizontal sweep of the scanning laser projector; and

record the distances and points during the second horizontal sweep as 3D image data, where locations of points are adjusted by the panning movement.

42. The method of claim 41 wherein determining distances to an object comprises creating laser light pulses with an abrupt change in amplitude.

43. The method of claim 42 wherein determining distances to an object further comprises differentiating reflected laser light pulses.

44. The method of claim 43 wherein determining distances to an object further comprises compressing differentiated signals.

45. The method of claim 43 wherein determining distances to an object further comprises amplifying differentiated signals to create differential output signals, and detecting when the differential output signals cross each other.