Use of Extended Detection Periods for Range Aliasing Detection and Mitigation in a Light Detection and Ranging (LIDAR) System

Patent metadata

Field	Value
Publication number	US-2019041503-A1
Application number	US-201715665591-A
Country	US
Kind code	A1
Filing date	Aug 1, 2017
Priority date	Aug 1, 2017
Publication date	Feb 7, 2019
Grant date	—

Abstract

A computing system may operate a LIDAR device to emit and detect light pulses in accordance with a time sequence including standard detection period(s) that establish a nominal detection range for the LIDAR device and extended detection period(s) having durations longer than those of the standard detection period(s). The system may then make a determination that the LIDAR detected return light pulse(s) during extended detection period(s) that correspond to particular emitted light pulse(s). Responsively, the computing system may determine that the detected return light pulse(s) have detection times relative to corresponding emission times of particular emitted light pulse(s) that are indicative of one or more ranges. Given this, the computing system may make a further determination of whether or not the one or more ranges indicate that an object is positioned outside of the nominal detection range, and may then engage in object detection in accordance with the further determination.

First claim

We claim:

1 . A method comprising:
operating, by a computing system, a Light Detection and Ranging (LIDAR) device to emit light pulses at emission times in accordance with an emission time sequence and to detect return light pulses in accordance with a detection time sequence, wherein the detection time sequence includes, for each emitted light pulse, a corresponding detection period for detection of a corresponding return light pulse, and wherein the corresponding detection periods comprise (i) one or more standard detection periods that establish a nominal detection range for the LIDAR device and (ii) one or more extended detection periods having respective durations that are longer than respective durations of the one or more standard detection periods; making a determination, by the computing system, that the LIDAR device detected one or more return light pulses during one or more of the extended detection periods that correspond to one or more particular emitted light pulses; in response to making the determination, determining, by the computing system, that the one or more detected return light pulses have detection times relative to corresponding emission times of the one or more particular emitted light pulses that are indicative of one or more ranges; making a further determination, by the computing system, of whether or not the one or more ranges indicate that an object is positioned outside of the nominal detection range; and engaging, by the computing system, in object detection in accordance with the further determination.

2 . The method of claim 1 , wherein the computing system has access to a fixed schedule that indicates timing to respectively initiate and end the one or more extended detection periods, and wherein operating the LIDAR device to detect return light pulses in accordance with the detection time sequence comprises operating the LIDAR device in accordance with the fixed schedule.

3 . The method of claim 1 , wherein operating the LIDAR device to detect return light pulses in accordance with the detection time sequence comprises operating the LIDAR device to respectively initiate the one or more extended detection periods in accordance with a periodic time sequence.

4 . The method of claim 1 , wherein the one or more extended detection periods correspond to one or more light pulses emitted by the LIDAR in one or more particular directions of travel.

5 . The method of claim 4 , wherein the one or more particular directions of travel comprise a direction of travel that is substantially parallel to a ground surface or is elevated away from the ground surface.

6 . The method of claim 1 , wherein making the further determination comprises:
making a further determination of whether or not the nominal detection range comprises the one or more ranges; if the further determination is that the nominal detection range comprises the one or more ranges, then, responsive to making the further determination, determining that the one or more ranges do not indicate that an object is positioned outside of the nominal detection range; and if the further determination is that the nominal detection range does not comprise the one or more ranges, then, responsive to making the further determination, determining that the one or more ranges indicate that an object is positioned outside of the nominal detection range.

7 . The method of claim 1 , wherein engaging in object detection in accordance with the further determination comprises:
if the further determination is that the one or more ranges indicate an object positioned outside of the nominal detection range, then, responsive to making the further determination, using at least the one or more ranges as a basis for generating a representation of an object positioned outside of the nominal detection range; and if the further determination is that the one or more ranges do not indicate an object positioned outside of the nominal detection range, then, responsive to making the further determination, using at least the one or more ranges as a basis for generating a representation of an object positioned within the nominal detection range.

8 . The method of claim 1 , wherein engaging in object detection in accordance with the further determination comprises:
if the further determination is that the one or more ranges indicate an object positioned outside of the nominal detection range, then, responsive to making the further determination, using at least the one or more ranges as a basis for determining a distance between the LIDAR device and an object positioned outside of the nominal detection range; and if the further determination is that the one or more ranges do not indicate an object positioned outside of the nominal detection range, then, responsive to making the further determination, using at least the one or more ranges as a basis for determining a distance between the LIDAR device and an object positioned within the nominal detection range.

9 . The method of claim 1 , wherein engaging in object detection in accordance with the further determination comprises:
if the further determination is that the one or more ranges indicate an object positioned outside of the nominal detection range, then, responsive to making the further determination, using at least the one or more ranges as a basis for identifying an object positioned outside of the nominal detection range; and if the further determination is that the one or more ranges do not indicate an object positioned outside of the nominal detection range, then, responsive to making the further determination, using at least the one or more ranges as a basis for identifying an object positioned within the nominal detection range.

10 . The method of claim 1 , further comprising:
determining, by the computing system, that the LIDAR device detected other return light pulses during corresponding detection periods for each of two or more emitted light pulses; and in response to determining that the LIDAR device detected other return light pulses, determining, by the computing system, that (i) the detected other return light pulses have detection times relative to corresponding emission times of a plurality of first emitted light pulses that are indicative of a first set of ranges and (ii) the detected other return light pulses have detection times relative to corresponding emission times of a plurality of second emitted light pulses that are indicative of a second set of ranges, wherein engaging in object detection in accordance with the further determination comprises:
based on the further determination, selecting between using the first set of ranges as a basis for object detection and using the second set of ranges as a basis for object detection; and
engaging in object detection in accordance with the selecting.

11 . The method of claim 10 , wherein determining that the LIDAR device detected other return light pulses during corresponding detection periods for each of two or more emitted light pulses comprises determining that the LIDAR device detected the other return light pulses during corresponding detection periods for each of the plurality of first emitted light pulses, and wherein selecting based on the further determination comprises:
if the further determination is that the one or more ranges indicate an object positioned outside of the nominal detection range, then, responsive to making the further determination, selecting use of the second set of ranges as a basis for object detection; and if the further determination is that the one or more ranges do not indicate an object positioned outside of the nominal detection range, then, responsive to ma

Assignees

• Waymo Llc

Inventors

• Shand Mark Alexander

Classifications

• G01S17/931

  of land vehicles · CPC title

• G01S17/42

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

• G01S17/10

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

• G01S7/4865 Primary

  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

• G01S17/89

  for mapping or imaging · CPC title