IP Library › Granted Patent US 11,467,288

Granted Patent B2

US 11,467,288 · App. 16/663,142 · Granted Oct 11, 2022

Lidar system and method of operation

Inventors: Jacob Hillard (Palo Alto, CA); John Dean (Palo Alto, CA); Jhoneldrick Millares (Palo Alto, CA); Rebecca Wong (Palo Alto, CA); Logan Herrera (Palo Alto, CA)

Assignee: Red Leader Technologies, Inc.

G01S17/89 G01S7/4804 G01S7/4815 G01S7/4816 G01S7/4817 G01S7/4865 G01S7/4911 G01S7/4914 G01S17/26

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Quick Facts

Patent No.: US 11,467,288
App. No.: 16/663,142
Granted: Oct 11, 2022
Kind: B2

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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 (96)

1. A method for environment mapping, comprising:

determining a code sequence;

after determining the code sequence, generating a periodic laser output representative of a periodic output signal that encodes the 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 wherein the code sequence is determined 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;

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; or 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 a second extremum of the filtered sample; 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 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.

12. 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.

13. A method for environment mapping, comprising:

before a time period, determining a first code sequence and a second code sequence;

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, wherein the first and second code sequences are determined such that a cross-correlation between the first and second periodic output signals is substantially zero;

throughout the 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.

14. The method of claim 13 , 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.

15. A method for environment mapping, comprising:

before a 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;

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 of the set of code sequences;