Lidar system with improved scanning speed for high-resolution depth mapping

• US 10,488,496 B2
• Filed: 11/03/2016
• Issued: 11/26/2019
• Est. Priority Date: 11/05/2015
• Status: Active Grant

• Current Assignee: Luminar Technologies, Inc.
• Original Assignee: Luminar Technologies, Inc.
• Inventors: Campbell, Scott R., Eichenholz, Jason M., Martin, Lane A., Weed, Matthew D.
• Primary Examiner(s): Baghdasaryan, Hovhannes
• Application Number:
  US15/342,728
• Publication Number:
  US 20170131388A1
• Time in Patent Office: 1,118 Days
• 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 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

A lidar system can include a light source that emits a pulse of light and a splitter that splits the pulse of light into two or more pulses of angularly separated light. The lidar system can also include a scanner configured to scan pulses of light along a scanning direction across a plurality of pixels located downrange from the lidar system. The lidar system can also include a detector array with a first detector and a second detector. The first and second detectors can be separated by a detector-separation distance along a direction corresponding to the scanning direction of the light pulses. The first detector can be configured to detect scattered light from the first pulse of light and the second detector can be configured to detect scattered light from the second pulse of light.

Claims

1. A lidar system comprising:

a light source configured to emit a plurality of pulses of light;

a splitter configured to split each of the emitted pulses of light into two or more pulses of angularly separated light comprising a first pulse of light and a second pulse of light that travel along separate, angularly separated paths;

a scanner configured to scan the emitted pulses of light, which are emitted by the light source and split by the splitter, along a scanning direction across a plurality of pixels located downrange from the lidar system, wherein scanning the emitted pulses of light comprises scanning a first light-source field of view associated with the first pulse of light and a second light-source field of view associated with the second pulse of light along the scanning direction across the plurality of pixels; and

a detector array comprising a first detector and a second detector separated by a detector-separation distance,

wherein the scanner is further configured to;

scan a field of view of the first detector along the scanning direction across the plurality of pixels so that (i) the first-detector field of view is offset from the first light-source field of view in a direction opposite the scanning direction and (ii) the first detector detects scattered light from the first pulse of light; and

scan a field of view of the second detector along the scanning direction across the plurality of pixels so that (i) the second-detector field of view is offset from the second light-source field of view in the direction opposite the scanning direction and (ii) the second detector detects scattered light from the second pulse of light.

2. The lidar system of claim 1, wherein:

the plurality of pixels comprises a first pixel, a second pixel, a third pixel, a fourth pixel, and a fifth pixel positioned along the scanning direction, wherein the first or second light-source field of view scans across the plurality of pixels and encounters the pixels in an order as follows;

first pixel, second pixel, third pixel, fourth pixel, fifth pixel.

3. The lidar system of claim 2, wherein the pulse of light is emitted at a time t₁ and the scanner is further configured to:

direct the first pulse of light toward the second pixel;

direct the second pulse of light toward the fifth pixel; and

scan a field of view of the first detector and a field of view of the second detector along the scanning direction across the plurality of pixels, wherein at time t₁;

the first-detector field of view at least partially overlaps the first pixel;

the first light-source field of view at least partially overlaps the second pixel;

the second detector field of view at least partially overlaps the fourth pixel; and

the second light-source field of view at least partially overlaps the fifth pixel.

4. The lidar system of claim 1, further comprising a processor configured to determine one or more distances to one or more targets based at least in part on a time of flight of the first pulse of light or a time of flight of the second pulse of light.

5. The lidar system of claim 1, wherein the scanner is configured to receive the first and second pulses of light from the splitter.

6. The lidar system of claim 1, wherein the splitter is configured to receive the emitted pulse of light from the scanner.

7. The lidar system of claim 1, wherein the splitter comprises a holographic element or a diffractive element.

8. The lidar system of claim 1, wherein the splitter is configured to split the emitted pulse of light into two pulses, wherein the first pulse of light and the second pulse of light each have approximately one-half of the energy or peak power of the emitted pulse of light.

9. The lidar system of claim 1, wherein:

the splitter is configured to split the emitted pulse of light into three pulses of angularly separated light;

the angularly separated pulses of light further comprise a third pulse; and

the detector array further comprises a third detector, wherein the scanner is further configured to scan a field of view of the third detector so that the third detector detects scattered light from the third pulse of light.

10. The lidar system of claim 1, wherein the angularly separated pulses of light are split along a direction corresponding to the scanning direction.

11. The lidar system of claim 1, wherein a separation distance between the first and second pulses of light at a maximum range of the lidar system corresponds to the detector-separation distance.

12. The lidar system of claim 1, wherein a separation distance between the first and second pulses of light at a maximum range of the lidar system corresponds to an odd number of pixels greater than or equal to three pixels.

13. The lidar system of claim 1, wherein the detector-separation distance corresponds to an odd number of pixels greater than or equal to three pixels.

14. The lidar system of claim 1, wherein the scanner is further configured to scan additional pulses of light, which are emitted by the light source and split by the splitter, along a reverse-scanning direction corresponding to a direction opposite the scanning direction.

15. The lidar system of claim 14, wherein:

the light source is further configured to emit an additional pulse of light while the scanner is scanning in the reverse-scanning direction;

the splitter is further configured to split the additional pulse of light into a third pulse of light and a fourth pulse of light, which are angularly separated; and

the detector array further comprises a third detector, wherein the scanner is further configured to;

scan the second-detector field of view so that the second detector detects scattered light from the fourth pulse of light; and

scan a field of view of the third detector so that the third detector detects scattered light from the third pulse of light.

16. The lidar system of claim 15, wherein the second and third detectors are separated by the detector-separation distance.

17. A method comprising:

emitting, by a light source of a lidar system, a plurality of pulses of light;

splitting, by a splitter, each of the emitted pulses of light into two or more pulses of angularly separated light comprising a first pulse of light and a second pulse of light that travel along separate, angularly separated paths;

scanning, by a scanner, the emitted pulses of light, which are emitted by the light source and split by the splitter, along a scanning direction across a plurality of pixels located downrange from the lidar system, wherein scanning the emitted pulses of light comprises scanning a first light-source field of view associated with the first pulse of light and a second light-source field of view associated with the second pulse of light along the scanning direction across the plurality of pixels;

scanning, by the scanner, a field of view of a first detector of a detector array along the scanning direction across the plurality of pixels so that the first-detector field of view is offset from the first light-source field of view in a direction opposite the scanning direction, wherein the detector array comprises the first detector and a second detector separated by a detector-separation distance;

detecting, by the first detector, scattered light from the first pulse of light;

scanning, by the scanner, a field of view of the second detector along the scanning direction across the plurality of pixels so that the second-detector field of view is offset from the second light-source field of view in the direction opposite the scanning direction; and

detecting, by the second detector, scattered light from the second pulse of light.

18. The method of claim 17, further comprising determining one or more distances to one or more targets based at least in part on a time of flight of the first pulse of light or a time of flight of the second pulse of light.

19. The method of claim 17, further comprising scanning additional pulses of light, which are emitted by the light source and split by the splitter, along a reverse-scanning direction corresponding to a direction opposite the scanning direction.

20. The method of claim 19, further comprising:

emitting, by the light source, an additional pulse of light while the scanner is scanning in the reverse-scanning direction;

splitting, by the splitter, the additional pulse of light into a third pulse of light and a fourth pulse of light, which are angularly separated;

detecting, by the second detector, scattered light from the fourth pulse of light; and

detecting, by a third detector of the detector array, scattered light from the third pulse of light.