Multispectral lidar system

• US 10,094,925 B1
• Filed: 04/02/2018
• Issued: 10/09/2018
• Est. Priority Date: 03/31/2017
• Status: Active Grant

• Current Assignee: Luminar Technologies, Inc.
• Original Assignee: Luminar Technologies, Inc.
• Inventors: LaChapelle, Joseph G.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US15/943,498
• Publication Number:
  US 20180284274A1
• Time in Patent Office: 190 Days
• Field of Search: 356 501
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• 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 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 3/8003 Diversity systems specially adapted for direction finding
• CPC Class Codes: G01S 5/22 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/28 takes precedence
• CPC Class Codes: G01S 5/28 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/483 Details of pulse systems
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers

Abstract

A multispectral lidar system includes a laser configured to emit a pulse of light including a first wavelength, scanner configured to direct the emitted pulse of light in accordance with a scan pattern, a receiver including a first detector and a second detector, and a controller. The first detector is configured to detect the emitted pulse of light scattered by a remote target, and the second detector is configured to detect light scattered or emitted by the remote target and including a second wavelength. The scanner provides, at any point in time, a fixed spatial relationship between the fields of view over which the light with the first wavelength and the second wavelength is received. A controller can determine a distance to the remote target and use this distance to modify a measurement of the property of the remote target based on the light detected by the second detector.

Claims

1. A multispectral lidar system comprising:

a laser configured to emit a pulse of light including a first wavelength;

a scanner configured to direct the emitted pulse of light in accordance with a scan pattern;

a receiver including;

a first detector configured to detect, over a first angular region defining a first detector field of view (FOV), the emitted pulse of light scattered by a remote target, and

a second detector configured to detect, over a second angular region defining a second detector FOV, light scattered or emitted by the remote target and including a second wavelength,

wherein the scanner provides, at any point in time, a fixed spatial relationship between the first detector FOV and the second detector FOV;

the lidar system further comprising;

a controller configured to (i) determine a distance to the remote target using the light detected by the first detector, (ii) generate a measurement of a property of the remote target based on the light detected by the second detector, and (iii) modify the generated measurement of the property of the remote target using the determined distance to the remote target.

2. The multispectral lidar system of claim 1, wherein the measurement of the property generated by the controller indicates a temperature of the remote target.

3. The multispectral lidar system of claim 2, wherein the second detector includes one or more thermal detector elements.

4. The multispectral lidar system of claim 2, wherein the second wavelength is one of (i) a mid-wave infrared or (ii) a long-wave infrared region.

5. The multispectral lidar system of claim 1, wherein the controller is further configured to (i) determine a reflectivity and/or an emissivity of the remote target using the light detected by the first detector, and (ii) modify the generated measurement of the property of the remote target using the determined reflectivity and/or emissivity.

6. The multispectral lidar system of claim 5, wherein the generated measurement includes a magnitude of the light in an infrared region emitted by the remote target and detected by the second detector, and wherein the controller is configured to (i) determine the emissivity of the remote target using the light detected by the first detector, and (ii) determine a temperature of the remote target using the determined emissivity and the magnitude of the light in the infrared region.

7. The multispectral lidar system of claim 1, wherein the controller is further configured to (i) determine a plurality of distances to points on a surface on the remote target using a plurality of respective pulses of light emitted by the laser and detected by the first detector, (ii) determine an orientation of the surface of the target relative to the multispectral lidar system using the determined plurality of distances, and (iii) modify the generated measurement of the property of the remote target using the determined orientation of the surface of the target.

8. The multispectral lidar system of claim 1, wherein the controller is configured to (i) generate, using the light detected by the first detector, first data having a first angular resolution, and (ii) generate, using the light detected by the second detector, second data having a second angular resolution, wherein the first angular resolution is larger than the second angular resolution.

9. The multispectral lidar system of claim 1, wherein the controller is configured to (i) generate, using the light detected by the first detector, first data having a first angular resolution, and (ii) generate, using the light detected by the second detector, second data having a second angular resolution, wherein the first angular resolution is smaller than the second angular resolution.

10. The multispectral lidar system of claim 1, further comprising:

an optical filtering element configured to (i) receive input light from the scanner, (ii) split the received input light into (i) a first component including the first wavelength and substantially free of the second wavelength, and (ii) a second component including the second wavelength and substantially free of the first wavelength, and (iii) direct the first component and the second component toward the first detector and the second detector, respectively.

11. The multispectral lidar system of claim 10, wherein the optical filtering element includes one of a reflection grating, a transmission grating, a prism, a grism, and interference filter, or a coating applied to a lens.

12. The multispectral lidar system of claim 1, wherein:

the first detector and the second detector are disposed on a same detector plane,

the first detector is positioned on the detector plane to detect the emitted pulse of light scattered by the remote target, when the remote target is within a maximum range of the multispectral lidar system, and

the second detector is positioned on the detector plane so that the emitted pulse of light scattered by the remote target is outside the second detector FOV.

13. The multispectral lidar system of claim 1, wherein the second detector includes a detector array made up of a plurality of identical detector elements.

14. The lidar system of claim 1, further comprising a second light source configured to emit light including the second wavelength, wherein the light detected by the second detector includes the light emitted by the second light source and scattered by the remote target.

15. A method in a multispectral lidar system for multispectral scanning, the method comprising:

emitting a pulse of light including a first wavelength;

directing the generated pulse of light in accordance with a scan pattern;

detecting the emitted pulse of light pulse of light scattered by a remote target, over a first angular region defining a first field of view (FOV);

detecting light scattered or emitted by the remote target and including a second wavelength, over a second angular region defining a second FOV, wherein the first FOV and the second FOV have a fixed spatial relationship in accordance with the scan pattern;

determining a distance to the remote target using the light detected over the first FOV;

generating a measurement of a property of the remote target based on the light detected over the second FOV; and

modifying the generated measurement of the property of the remote target using the determined distance to the remote target.

16. The method of claim 15, wherein generating the measurement of the property of the remote target includes generating a measurement of a temperature of the remote target.

17. The method of claim 16, wherein detecting the light including the second wavelength includes using one or more thermal detector elements.

18. The method of claim 16, wherein the second wavelength is one of (i) a mid-wave infrared or (ii) a long-wave infrared region.

19. The method of claim 15, further comprising:

determining a reflectivity and/or an emissivity of the remote target using the detected light that includes the first wavelength; and

modifying the generated measurement of the property of the remote target using the determined reflectivity and/or emissivity.

20. The method of claim 15, wherein the generated measurement includes a magnitude of the light in an infrared region emitted by the remote target and detected over the second FOV, the method further comprising:

determining the emissivity of the remote target using the light detected over the first FOV; and

determining a temperature of the remote target using the determined emissivity and the magnitude of the light in the infrared region.

21. The method of claim 20, wherein determining the temperature of the remote target using the determined emissivity and the magnitude of the light in the infrared region includes using a look-up table.

22. The method of claim 15, further comprising:

determining a plurality of distances to points on a surface on the remote target using a plurality of respective pulses of light emitted with the first wavelength and detected over the first FOV;

determining an orientation of the surface of the target relative to the multispectral lidar system using the determined plurality of distances; and

modifying the generated measurement of the property of the remote target using the determined orientation of the surface of the target.

23. The method of claim 15, further comprising:

generating, using the light detected over the first FOV, first data having a first angular resolution; and

generating, using the light detected over the second FOV, second data having a second angular resolution, wherein the first angular resolution is larger than the second angular resolution.

24. The method of claim 15, further comprising:

generating, using the light detected over the first FOV, first data having a first angular resolution; and

generating, using the light detected over the second FOV, second data having a second angular resolution, wherein the first angular resolution is smaller than the second angular resolution.

25. The method of claim 15, further comprising emitting light including the second wavelength, wherein the light detected over the second FOV includes the emitted light with the second wavelength and scattered by the remote target.