Time division multiplexing of multiple wavelengths for high resolution scanning time of flight 3D imaging

Patent metadata

Field	Value
Publication number	US-10859704-B2
Application number	US-201815865115-A
Country	US
Kind code	B2
Filing date	Jan 8, 2018
Priority date	Jan 8, 2018
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

Laser light pulses of at least two different wavelengths are reflected off a scanning mirror. A first time-of-flight distance measurement circuit receives reflected light pulses of a first wavelength and determines distances. A second time-of-flight distance measurement circuit receives reflected light pulses of a second wavelength and determines distances. The laser light pulses of different wavelengths may be interleaved in time to increase resolution. The laser light pulses of different wavelengths may also be used for detecting safety violations and/or power control.

First claim

What is claimed is:

1. An apparatus comprising:
a first laser light source to emit laser light pulses of a first wavelength;
a second laser light source to emit laser light pulses of a second wavelength;
at least one scanning mirror to reflect and scan the laser light pulses from the first and second laser light sources;
a first time-of-flight measurement circuit to receive reflections of, and to determine times-of-flight of, laser light pulses of the first wavelength, wherein the first time-of-flight measurement circuit exhibits a first processing time that influences a minimum pulse spacing of the laser light pulses of the first wavelength;
a second time-of-flight measurement circuit to receive reflections of, and to determine times-of-flight of, laser light pulses of the second wavelength, wherein the second time-of-flight measurement circuit exhibits a second processing time that influences a minimum pulse spacing of the laser light pulses of the second wavelength; and
a pulse timing circuit to cause laser light pulses of the first and second wavelengths to be interleaved in time to decrease an effective minimum pulse spacing and increase spatial measurement resolution.

2. The apparatus of claim 1 wherein the first time-of-flight measurement circuit comprises:
a first photodetector to detect reflected laser light pulses of the first wavelength;
a first differentiator coupled to the first photodetector to differentiate detected pulses;
a first amplifier to receive differentiated detected pulses from the first differentiator and to generate first differential output signals;
a first detection circuit to detect when the first differential output signals cross each other; and
a first integrator responsive to the first detection circuit for time measurement.

3. The apparatus of claim 2 wherein the second time-of-flight measurement circuit comprises:
a second photodetector to detect reflected laser light pulses of the second wavelength;
a second differentiator coupled to the second photodetector to differentiate detected pulses;
a second amplifier to receive differentiated detected pulses from the second differentiator and to generate second differential output signals;
a second detection circuit to detect when the second differential output signals cross each other; and
a second integrator responsive to the second detection circuit for time measurement.

4. The apparatus of claim 1 wherein the first and second time-of-flight measurement circuits each include a comparator to compare a received pulse amplitude to a threshold.

5. The apparatus of claim 1 wherein the first and second laser light sources emit infrared light.

6. The apparatus of claim 5 further comprising:
at least one laser light source to produce laser light pulses in the visible spectrum; and
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.

7. The apparatus of claim 1 further comprising a third laser light source to emit laser light pulses of a third wavelength.

8. An apparatus comprising:
a first laser light source to emit laser light pulses of a first wavelength;
a second laser light source to emit laser light pulses of a second wavelength;
a plurality of first time-of-flight measurement circuits to receive reflections of, and to determine times-of-flight of, laser light pulses of the first wavelength, wherein each of the plurality of first time-of-flight measurement circuits exhibits a first processing time that influences a minimum pulse spacing of the laser light pulses of the first wavelength;
a plurality of second time-of-flight measurement circuits to receive reflections of, and to determine times-of-flight of, laser light pulses of the second wavelength, wherein each of the plurality of second time-of-flight measurement circuits exhibits a second processing time that influences a minimum pulse spacing of the laser light pulses of the second wavelength; and
a pulse timing circuit to cause laser light pulses of the first and second wavelengths to be interleaved in time to decrease an effective minimum pulse spacing and increase spatial measurement resolution.

9. The apparatus of claim 8 further comprising at least one scanning mirror to reflect and scan laser light pulses from the first and second laser light sources.

10. The apparatus of claim 9 wherein the first and second laser light sources emit light pulses in the nonvisible spectrum.

11. The apparatus of claim 10 wherein the first and second laser light sources emit infrared light of different wavelengths.

12. The apparatus of claim 10 further comprising at least one laser light source to produce light in the visible spectrum.

13. The apparatus of claim 12 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.

14. A 3D imaging device comprising:
a scanning mirror to scan first infrared laser light pulses having a first wavelength and second infrared laser light pulses having a second wavelength in at least one dimension, wherein the first and second infrared laser light pulses are interleaved in time;
a first time of flight distance measurement circuit to determine distances traveled by reflected infrared laser light pulses having the first wavelength, wherein the first time-of-flight distance measurement circuit exhibits a first processing time that influences a minimum pulse spacing of the laser light pulses of the first wavelength;
a second time of flight distance measurement circuit to determine distances traveled by reflected infrared laser light pulses having the second wavelength, wherein the second time-of-flight distance measurement circuit exhibits a second processing time that influences a minimum pulse spacing of the laser light pulses of the second wavelength; and
a pulse timing circuit to cause the laser light pulses of the first and second wavelengths to be interleaved in time to decrease an effective minimum pulse spacing and increase spatial measurement resolution.

15. The 3D imaging device of claim 14 wherein the scanning mirror is configured to scan in two dimensions.

16. The 3D imaging device of claim 14 wherein each of the first and second time-of-flight distance measurement circuits comprises a photodetector, a differentiator, a cross point detector and an integrator.

17. The 3D imaging device of claim 14 wherein each of the first and second time-of-flight distance measurement circuits comprises a photodetector and a comparator to compare an amplitude of reflected infrared laser light pulses to a threshold.

18. The 3D imaging device of claim 17 further comprising at least one visible laser light source to produce visible laser light pulses.

19. The 3D imaging device of claim 18 further comprising image processing circuitry to drive the at least one visible laser light source to produce the visible laser light pulses to display an image with visible light while performing distance measurements with infrared light.

Assignees

• Microvision Inc

Inventors

• Viswanathan P Selvan
• Xue Bin

Classifications

• G01S17/10 Primary

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/4868

  Controlling received signal intensity or exposure of sensor · CPC title

• G01S7/4815

  using multiple transmitters · CPC title

• G01S17/89 Primary

  for mapping or imaging · CPC title

• G01S7/4865

  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 title