LIDAR SYSTEM AND METHOD OF OPERATION

• US 20200132847A1
• Filed: 10/24/2019
• Published: 04/30/2020
• Est. Priority Date: 10/24/2018
• Status: Active Grant

• Current Assignee: Red Leader Technologies, Inc.
• Original Assignee: Red Leader Technologies, Inc.
• Inventors: Hillard, Jacob, Dean, John, Millares, Jhoneldrick, Wong, Rebecca, Herrera, Logan
• Granted Patent: US 11,467,288 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 17/26 wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4804 Auxiliary means for detecting or identifying lidar signals or the like, e.g. laser illuminators
• CPC Class Codes: G01S 7/4815 using multiple transmitters
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4865 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 Class Codes: G01S 7/4911 Transmitters
• CPC Class Codes: G01S 7/4914 of detector arrays, e.g. charge-transfer gates
• CPC Class Codes: G01S 7/493 Extracting wanted echo signals

Abstract

A LIDAR system, preferably including one or more: optical emitters, optical detectors, beam directors, and/or processing modules. A method of LIDAR system operation, preferably including: determining a signal, outputting the signal, receiving a return signal, and/or analyzing the return signal.

Claims

1. A method for environment mapping, comprising:

generating a periodic laser output representative of a periodic output signal that encodes a code sequence, comprising modulating a substantially continuous-wave carrier signal based on the code sequence;

throughout a time period, continuously transmitting the periodic laser output into an environment;

during the time period, at an optical sensor, receiving a return signal comprising a reflection, from an object within the environment, of the periodic laser output;

determining a sample indicative of a contiguous time window of the return signal, wherein a duration of the contiguous time window is greater than a period of the periodic output signal;

generating a filtered sample, comprising filtering the sample based on the code sequence;

based on the filtered sample;

determining an extremum of the filtered sample; and

determining a delay time associated with the extremum; and

based on the delay time, determining a relative location of the object.

2. The method of claim 1, wherein filtering the sample based on the code sequence comprises applying, to the sample, a matched filter for the periodic output signal.

3. The method of claim 2, wherein applying the matched filter comprises determining at least one of:

a circular convolution of the sample with a time-reversed version of the periodic output signal; and

a circular convolution of the periodic output signal with a time-reversed version of the sample.

4. The method of claim 1, wherein determining the delay time comprises:

determining an interpolated sub-sample comprising the extremum; and

determining the delay time based on the interpolated sub-sample.

5. The method of claim 4, wherein determining the interpolated sub-sample comprises performing a continuous curve interpolation.

6. The method of claim 1, wherein the return signal further comprises a second reflection, from a second object within the environment, of the periodic laser output, the method further comprising:

based on the filtered sample, determining a second delay time associated with the second object; and

based on the second delay time, determining a relative location of the second object.

7. The method of claim 6, further comprising, before determining the second delay time, determining a first peak region associated with the extremum;

wherein determining the second delay time comprises;

determining a second extremum of the filtered sample, wherein the second extremum is not within the first peak region, wherein a magnitude of the extremum is greater than a magnitude of the second extremum; and

determining the second delay time based on the second extremum.

8. The method of claim 1, further comprising:

at the optical sensor, after receiving the return signal, receiving a second return signal comprising a second reflection, from a second object within the environment, of the periodic laser output;

determining a second sample indicative of a second contiguous time window of the second return signal;

generating a second filtered sample, comprising filtering the second sample based on the code sequence;

based on the second filtered sample, determining a second delay time associated with the second extremum; and

based on the second delay time, determining a relative location of the second object.

9. The method of claim 1, further comprising:

generating a second periodic laser output encoding a second periodic output signal, comprising modulating a second substantially continuous-wave carrier signal based on a second code sequence;

throughout the time period, continuously transmitting the second periodic laser output into the environment;

generating a second filtered sample, comprising filtering the sample based on the second code sequence, wherein the return signal further comprises a second reflection, from a second object within the environment, of the second periodic laser output;

based on the second filtered sample;

determining a second extremum of the second filtered sample; and

determining a second delay time associated with the second extremum; and

based on the second delay time, determining a relative location of the second object.

10. The method of claim 1, wherein modulating the substantially continuous-wave carrier signal based on the code sequence comprises encoding the code sequence using a phase-shift keying.

11. The method of claim 1, further comprising, before generating the periodic laser output, determining the code sequence such that a cross-correlation between the periodic output signal and other optical signals received at the optical sensor is less than a threshold value.

12. The method of claim 11, further comprising, before determining the code sequence:

selecting a candidate code sequence;

generating a candidate laser output representative of a candidate output signal that encodes the candidate code sequence;

transmitting the candidate laser output;

at the optical sensor, receiving a test signal; and

based on the test signal, determining that a test cross-correlation between the candidate output signal and the other optical signals is greater than the threshold value;

wherein the code sequence is determined in response to determining that the test cross-correlation is greater than the threshold value.

13. The method of claim 1, further comprising:

before the time period;

based on a first set of desired performance metrics, determining a first sequence length, wherein the first set of desired performance metrics comprises at least one of;

accuracy, range, resolution, and latency; and

determining the code sequence based on the first sequence length, wherein a length of the code sequence is equal to the first sequence length;

based on the return signal, determining a second sequence length;

determining a second code sequence based on the second sequence length, wherein a length of the second code sequence is equal to the second sequence length;

generating a second periodic laser output representative of a second periodic output signal that encodes the second code sequence, comprising modulating the substantially continuous-wave carrier signal based on the second code sequence;

throughout a second time period following the time period, continuously transmitting the second periodic laser output into the environment;

during the second time period, at the optical sensor, receiving a second return signal comprising a second reflection, from the object, of the second periodic laser output;

determining a second sample indicative of a second contiguous time window of the second return signal;

generating a second filtered sample, comprising filtering the second sample based on the second code sequence;

based on the second filtered sample;

determining a second extremum of the second filtered sample; and

determining a second delay time associated with the second extremum; and

based on the second delay time, determining an updated relative location of the object.

14. A method for environment mapping, comprising:

generating a first periodic optical output representative of a first periodic output signal, comprising modulating a first substantially continuous-wave carrier signal based on a first code sequence;

generating a second periodic optical output representative of a second periodic output signal, comprising modulating a second substantially continuous-wave carrier signal based on a second code sequence;

throughout a time period, continuously transmitting the first and second periodic optical outputs into an environment;

during the time period, at an optical sensor, receiving a return signal, the return signal comprising;

a first reflection, from a first object within the environment, of the first periodic optical output; and

a second reflection, from a second object within the environment, of the second periodic optical output;

determining a sample by selecting a contiguous time window of the return signal;

generating a first filtered sample, comprising filtering the sample based on the first code sequence;

determining a first delay time associated with the first filtered sample;

based on the first delay time, determining a relative location of the first object;

generating a second filtered sample, comprising filtering the sample based on the second code sequence;

determining a second delay time associated with the second filtered sample; and

based on the second delay time, determining a relative location of the second object.

15. The method of claim 14, further comprising, before the time period, determining the first and second code sequences such that a cross-correlation between the first and second periodic output signals is substantially zero.

16. The method of claim 15, further comprising, before the time period, determining a sequence length, wherein the lengths of the first and second code sequences are each equal to the sequence length.

17. The method of claim 14, further comprising, before the time period, determining a set of code sequences, each code sequence of the set associated with a respective periodic output signal that encodes the code sequence, wherein:

determining the set of code sequences comprises performing a stochastic optimization such that, for each pair of code sequences of the set, a respective cross-correlation between the respective periodic output sequences associated with the code sequences of the pair is less than a threshold value; and

the set of code sequences comprises the first and second code sequences.

18. The method of claim 14, wherein:

the first periodic optical output is transmit into the environment by a first laser; and

the second periodic optical output is transmit into the environment by a second laser.

19. The method of claim 14, wherein the optical sensor comprises a photodiode, wherein the return signal is received at the photodiode.

20. The method of claim 18, wherein the first and second reflections are received at the photodiode concurrently.