Interlaced scan patterns for lidar system

Patent metadata

Field	Value
Publication number	US-11415676-B2
Application number	US-201816155337-A
Country	US
Kind code	B2
Filing date	Oct 9, 2018
Priority date	Oct 9, 2017
Publication date	Aug 16, 2022
Grant date	Aug 16, 2022

Abstract

In one embodiment, a lidar system includes a light source configured to emit pulses of light and a scanner configured to scan at least a portion of the emitted pulses of light along an interlaced scan pattern. The scanner includes a first scanning mirror configured to scan the portion of the emitted pulses of light substantially parallel to a first scan axis to produce multiple scan lines of the interlaced scan pattern, where each scan line is oriented substantially parallel to the first scan axis. The scanner also includes a second scanning mirror configured to distribute the scan lines along a second scan axis that is substantially orthogonal to the first scan axis, where the scan lines are distributed in an interlaced manner.

First claim

What is claimed is:

1. A lidar system comprising:
a light source configured to emit pulses of light;
a scanner configured to scan at least a portion of the emitted pulses of light along an interlaced scan pattern, wherein the scanner comprises:
a first scanning mirror configured to scan the portion of the emitted pulses of light substantially parallel to a first scan axis to produce a plurality of scan lines of the interlaced scan pattern, wherein each scan line is oriented substantially parallel to the first scan axis; and
a second scanning mirror configured to distribute the scan lines along a second scan axis that is substantially orthogonal to the first scan axis, wherein the scan lines are distributed in an interlaced manner, wherein the interlaced scan pattern is an n-fold interlaced scan pattern comprising n sub-scans, wherein:
n is an integer greater than or equal to 2;
each sub-scan comprises two or more of the scan lines of the interlaced scan pattern;
the n sub-scans are scanned sequentially wherein a first sub-scan of the n sub-scans is scanned prior to a second sub-scan;
adjacent scan lines of a particular sub-scan are separated from one another by (n−1) intermediate scan lines of other sub-scans;
the n-fold interlaced scan pattern is scanned in a time period ΔT;
full-resolution point clouds based on the n-fold interlaced scan pattern are produced at a frequency of approximately 1/ΔT; and
partial-resolution point clouds based on each of the sub-scans are produced at a frequency of approximately n/ΔT; and

a receiver configured to detect at least a portion of the scanned pulses of light scattered by a target located a distance from the lidar system.

2. The lidar system of claim 1 , wherein:
n=2;
the interlaced scan pattern is a 2-fold interlaced scan pattern, wherein the first sub-scan comprises a plurality of even scan lines and the second sub-scan comprises a plurality of odd scan lines;
each pair of adjacent even scan lines is separated by an odd scan line; and
each pair of adjacent odd scan lines is separated by an even scan line.

3. The lidar system of claim 2 , wherein:
the odd scan lines are used to produce a first partial-resolution point cloud;
the even scan lines are used to produce a second partial-resolution point cloud; and
the first and second partial-resolution point clouds are combined to produce a full-resolution point cloud.

4. The lidar system of claim 1 , wherein:
the other sub-scans comprise (n−1) sub-scans of the n sub-scans which are different from the particular sub-scan; and
the (n−1) intermediate scan lines located between the adjacent scan lines of the particular sub-scan comprise one scan line from each of the other sub-scans.

5. The lidar system of claim 1 , wherein:
the interlaced scan pattern comprises N scan lines; and
each sub-scan comprises approximately N/n scan lines.

6. The lidar system of claim 1 , wherein:
n=2; and
the interlaced scan pattern is a 2-fold interlaced scan pattern comprising the first sub-scan and the second sub-scan.

7. The lidar system of claim 1 , wherein:
n=4; and
the interlaced scan pattern is a 4-fold interlaced scan pattern comprising four sub-scans.

8. The lidar system of claim 1 , wherein the scanner is further configured to scan the portion of the emitted pulses of light along a non-interlaced scan pattern, wherein the scan lines are scanned sequentially, wherein:
the scan lines comprise a first scan line, a second scan line, and a third scan line, wherein the second scan line is disposed between the first and third scan lines; and
during the scan of the non-interlaced scan pattern, the second scan line is scanned after the first scan line is scanned and the third scan line is scanned after the second scan line is scanned.

9. The lidar system of claim 8 , wherein the interlaced scan pattern is configured to provide a higher frame rate than the non-interlaced scan pattern.

10. The lidar system of claim 8 , further comprising a processor configured to instruct the scanner to switch from scanning along the non-interlaced scan pattern to scanning along the interlaced scan pattern.

11. The lidar system of claim 10 , wherein the processor is configured to instruct the scanner to switch from the non-interlaced scan pattern to the interlaced scan pattern based at least in part on a driving condition of a vehicle in which the lidar system is operating, wherein the driving condition comprises determining that the target is within a particular threshold distance of the lidar system or that the target has a speed with respect to the lidar system above a particular threshold speed.

12. The lidar system of claim 1 , wherein:
the first scanning mirror is driven repeatedly in a back-and-forth motion by a galvanometer scanner; and
each scan line corresponds to a single forward or backward motion of the galvanometer scanner.

13. The lidar system of claim 1 , wherein the first scanning mirror is a polygon mirror comprising two or more reflective surfaces, wherein:
the polygon mirror is configured to continuously rotate in one direction about a rotation axis of the polygon mirror; and
the portion of the emitted pulses of light are reflected sequentially from the reflective surfaces as the polygon mirror is rotated, resulting in the portion of the emitted pulses of light being scanned substantially parallel to the first scan axis to produce the plurality of scan lines, wherein each scan line corresponds to a reflection from one of the reflective surfaces.

14. The lidar system of claim 1 , further comprising a processor configured to determine the distance from the lidar system to the target based at least in part on a round-trip time of flight for an emitted pulse of light to travel from the lidar system to the target and back to the lidar system.

15. The lidar system of claim 1 , wherein the interlaced scan pattern is a dual-direction interlaced scan pattern wherein the first sub-scan is scanned in a first direction and the second sub-scan is scanned in a second direction opposite the first direction.

16. The lidar system of claim 15 , wherein the first direction is a top-to-bottom direction and the second direction is a bottom-to-top direction.

17. The lidar system of claim 1 , wherein:
the time period ΔT is approximately 100 ms;
the full-resolution point clouds are produced at a frequency of approximately 10 Hz;
n is equal to 4, so that the interlaced scan pattern is a 4-fold interlaced scan pattern comprising 4 sub-scans; and
partial-resolution point clouds based on each of the sub-scans are produced at a frequency of approximately 40 Hz.

18. A method comprising:
emitting, by a light source of a lidar system, pulses of light;
scanning, by a scanner of the lidar system, at least a portion of the emitted pulses of light along an interlaced scan pattern, comprising:
scanning the portion of the emitted pulses of light substantially parallel to a first scan axis to produce a plurality of scan lines of the interlaced scan pattern, wherein each scan line is oriented substantially parallel to the first scan axis; and
distributing the scan lines along a second scan axis that is substantially orthogonal to the first scan axis, wherein the scan lines are distributed in an interlaced manner, wherein the interlaced scan pattern is an n-fold interlaced scan pattern comprising n sub-scans, wherein:
n is an integer greater than or equal to 2;
each sub-scan comprises two or more of the scan lines of the interlaced scan pattern;
the n sub-scans are sc

Assignees

• Luminar Llc

Inventors

• Danziger Eric C

Classifications

• 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

• G01S7/4808

  Evaluating distance, position or velocity data · CPC title

• G01S7/4817 Primary

  relating to scanning · CPC title

• G01S17/89

  for mapping or imaging · CPC title

• G01S17/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title