Identifying and/or removing ghost detections from lidar sensor output

Patent metadata

Field	Value
Publication number	US-11500075-B2
Application number	US-201916276327-A
Country	US
Kind code	B2
Filing date	Feb 14, 2019
Priority date	Feb 1, 2019
Publication date	Nov 15, 2022
Grant date	Nov 15, 2022

Abstract

A LIDAR system that identifies, from a channel output, a false positive return and/or suppressing a corresponding false positive detection caused, in some cases, a strong reflection by a highly reflective surface that caused light to leak from a first channel to a second channel. The LIDAR system described herein may identify, as a false return, a return detected in the second channel that has an intensity that is much less than a return in the first channel and indicates a distance that is the same or very close to a distance indicated the return in the first channel. Based at least in part on identifying a return as a false return, the LIDAR system may suppress a false detection associated with the false return by modifying a detection threshold.

First claim

What is claimed is:

1. A method comprising:
receiving, from a first sensor associated with a first channel of a LIDAR device, a first output signal associated with a first distance;
receiving, at a second sensor associated with a second channel of the LIDAR device, a second output signal associated with a second distance;
identifying, as a first return, a first portion of the first output signal that meets or exceeds a detection threshold;
identifying a second portion of the second output signal as comprising a false positive return based at least in part on:
determining that the second distance is within a threshold distance of the first distance; and
determining that a difference between a first intensity of the first output signal and a second intensity of the second output signal meets or exceeds a threshold difference;

outputting, as a positive detection, a first distance measurement based at least in part on identifying the first return; and
discarding a second distance measurement associated with the second output signal based at least in part on identifying the second portion of the second output signal as comprising a false positive return.

2. The method of claim 1 , wherein identifying the second portion of the second output signal as comprising a false positive return is further based at least in part on determining that at least one of:
the first sensor is within a threshold physical distance of the second sensor;
a portion of the first output signal and a portion of the second output signal were generated substantially simultaneously; or
the first intensity of the first portion meets or exceeds an upper detection threshold, wherein the upper detection threshold is greater than the detection threshold.

3. The method of claim 1 , wherein discarding the second distance measurement is based at least in part on at least one of:
increasing the detection threshold of the second channel;
increasing, based at least in part on at least one of the first intensity or the second intensity, the detection threshold of the second channel; or
increasing the detection threshold of the first channel and the second channel.

4. The method of claim 1 , wherein the difference comprises a ratio, and
further wherein the threshold difference comprises a percentage of the first return.

5. A system comprising:
a first sensor associated with a first channel;
a second sensor associated with a second channel;
one or more processors configured to perform operations comprising:
receiving, from the first sensor, a first return signal associated with a first distance;
receiving, from the second sensor, a second return signal associated with a second distance;
identifying at least a portion of the second return signal as comprising a false positive return based at least in part on:
determining that the second distance is within a threshold distance of the first distance; and
determining that a difference between a first intensity of the first return signal and a second intensity of the second return signal meets or exceeds a threshold difference.

6. The system of claim 5 , the operations further comprising modifying a detection threshold, to obtain a modified detection threshold, associated with at least the second channel based at least in part on the identifying, and
wherein modifying the detection threshold comprises at least one of:
increasing the detection threshold for the second channel;
increasing the detection threshold for the second channel based on the second distance;
increasing, based at least in part on at least one of the first intensity or the second intensity, the detection threshold of the second channel; or
increasing the detection threshold in of the first channel and the second channel.

7. The system of claim 5 , wherein the difference comprises a ratio of a portion of the first return signal to a portion of the second return signal.

8. The system of claim 5 , wherein the operations further comprise:
outputting a confidence associated with the false positive return, the confidence based at least in part on one or more of:
a distance between of the first sensor and the second sensor;
a ratio of a portion of the first return signal to a portion of the second return signal, or
a ration of first time that the first sensor was active to a second time that the second sensor was active.

9. The system of claim 5 , wherein identifying at least the portion of the second return signal as comprising a false positive return is further based at least in part on determining that at least one of:
the first sensor is within a threshold physical distance of second sensor;
a portion of the first return signal was generated substantially simultaneously with a portion of the second return signal; or
the first intensity meets or exceeds an upper detection threshold, wherein the upper detection threshold is greater than the detection threshold.

10. The system of claim 5 further comprising:
a first emitter associated with the first channel, the first emitter configured to emit a first light pulse based at least in part on activation of the first channel; and
a second emitter associated with the second channel, the second emitter configured to emit a second light pulse based at least in part on activation of the second channel.

11. The system of claim 6 , wherein modifying the detection threshold comprises modifying the detection threshold within a range of times.

12. The system of claim 6 , wherein the operations further comprise:
determining that at least a first portion of the first return signal meets or exceeds the modified detection threshold;
outputting, as a positive detection, a first distance measurement associated with the first portion based at least in part on determining that the first portion meets or exceeds the modified detection threshold;
determining that the portion of the second return signal is less than the modified detection threshold; and
refraining from outputting a second distance measurement associated with the portion of the second return signal.

13. A non-transitory computer-readable medium storing processor-executable instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising:
receiving, from a first sensor, a first return signal associated with a first distance;
receiving, from a second sensor, a second return signal associated with a second distance; and
identifying at least a portion of the second return signal as comprising a false positive return based at least in part on:
determining that the second distance is within a threshold distance of the first distance; and
determining that a difference between a first intensity of the first return signal and a second intensity of the second return signal meets or exceeds a threshold difference.

14. The non-transitory computer-readable medium of claim 13 , wherein the operations further comprise:
modifying a detection threshold, to obtain a modified detection threshold, based at least in part on the identifying the at least a portion of the second return signal as comprising a false positive return.

15. The non-transitory computer-readable medium of claim 14 , wherein modifying the detection threshold comprises:
increasing the detection threshold for a second channel associated with the second sensor;
increasing, based at least in part on at least one of the first intensity or the second intensity, the detection threshold for the second channel; or
increasing the detection threshold for a first channel associated w

Assignees

• Zoox Inc

Inventors

• Bhaskaran Sreevatsan
• Ferdowsi Mehran
• Mcmichael Ryan
• Subasingha Subasingha Shaminda

Classifications

• H04B10/503

  Laser transmitters · CPC title

• G01S17/931

  of land vehicles · CPC title

• G01S7/4815

  using multiple transmitters · CPC title

• G01S7/4873 Primary

  by deriving and controlling a threshold value · CPC title

• G01S7/4863 Primary

  Detector arrays, e.g. charge-transfer gates · CPC title