Lidar system and method of operation

1. A method for environment mapping, comprising:

selecting a set of phase-bounded low cross-correlation codes (PB-LCCs), the set of PB-LCCs comprising a first PB-LCC and a second PB-LCC, wherein the set of PB-LCCs defines a phase bound;

generating a first optical output representative of a first output signal, comprising modulating a first substantially continuous-wave carrier signal based on the first PB-LCC;

generating a second optical output representative of a second output signal, comprising modulating a second substantially continuous-wave carrier signal based on the second PB-LCC;

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

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 optical output; and

a second reflection, from a second object within the environment, of the second 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 PB-LCC;

determining a first phase delay associated with the first filtered sample, wherein the first phase delay is within the phase bound;

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

generating a second filtered sample, comprising filtering the sample based on the second PB-LCC;

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.

2. The method of claim 1 , further comprising:

generating a third optical output representative of a third output signal, comprising modulating a third substantially continuous-wave carrier signal based on a third PB-LCC of the set of PB-LCCs;

throughout the time period, concurrent with transmitting the first and second optical outputs into the environment, transmitting the third optical output into the environment;

generating a third filtered sample, comprising filtering the sample based on the third PB-LCC;

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

based on the third delay time, determining a relative location of a third object within the environment; wherein the return signal further comprises a third reflection, from the third object, of the third optical output.

3. The method of claim 2 , further comprising:

generating a fourth optical output representative of a fourth output signal, comprising modulating a fourth substantially continuous-wave carrier signal based on a fourth PB-LCC of the set of PB-LCCs;

throughout the time period, concurrent with transmitting the first, second, and third optical outputs into the environment, transmitting the fourth optical output into the environment;

generating a fourth filtered sample, comprising filtering the sample based on the fourth PB-LCC;

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

based on the fourth delay time, determining a relative location of a fourth object within the environment; wherein the return signal further comprises a fourth reflection, from the fourth object, of the fourth optical output.

4. The method of claim 3 , wherein the set of PB-LCCs defines a set of pairwise cross-correlations, the method further comprising:

based on the set of pairwise cross-correlations and the second, third, and fourth filtered samples, correcting the first filtered sample for interference associated with the second, third, and fourth reflections;

based on the set of pairwise cross-correlations and the first, third, and fourth filtered samples, correcting the second filtered sample for interference associated with the first, third, and fourth reflections;

based on the set of pairwise cross-correlations and the first, second, and fourth filtered samples, correcting the third filtered sample for interference associated with the first, second, and fourth reflections; and

based on the set of pairwise cross-correlations and the first, second, and third filtered samples, correcting the fourth filtered sample for interference associated with the first, second, and third reflections.

5. The method of claim 1 , wherein the first and second PB-LCCs define a cross-correlation, the method further comprising:

based on the cross-correlation and the second filtered sample, correcting the first filtered sample for interference associated with the second reflection; and

based on the cross-correlation and the first filtered sample, correcting the second filtered sample for interference associated with the first reflection.

6. The method of claim 5 , further comprising:

based on the cross-correlation and the corrected second filtered sample, further correcting the corrected first filtered sample for interference associated with the second reflection; and

based on the cross-correlation and the corrected first filtered sample, further correcting the corrected second filtered sample for interference associated with the first reflection.

7. The method of claim 1 , wherein filtering the sample based on the first PB-LCC comprises applying a matched filter, associated with the first PB-LCC, to the sample.

8. The method of claim 7 , wherein applying the matched filter is performed in the frequency domain.

9. The method of claim 7 , wherein:

the first PB-LCC is a binary code; and

applying the matched filter is performed in the time domain.

10. The method of claim 9 , wherein applying the matched filter to a signal comprises:

generating a set of delayed copies of the signal based on a set of delay times, comprising, for each delay time of the set of delay times, generating, based on the delay time, a respective delayed copy of the set of delayed copies, wherein the set of delay times is indicative of the first PB-LCC; and

determining a sum of the delayed copies of the set.

11. The method of claim 1 , wherein the first optical output is substantially periodic and the second optical output is substantially periodic.

12. The method of claim 11 , wherein:

concurrently transmitting the first and second optical outputs into the environment comprises transmitting the first and second optical outputs substantially continuously throughout the time period; and

the return signal is received at the optical sensor during the time period.

13. The method of claim 1 , wherein modulating the first substantially continuous-wave carrier signal based on the first PB-LCC comprises performing optical frequency modulation.

14. The method of claim 1 , wherein modulating the first substantially continuous-wave carrier signal based on the first PB-LCC comprises performing amplitude modulation.

15. The method of claim 1 , wherein determining the first phase delay comprises:

determining an extremum of the first filtered sample; and

determining the phase delay based on the extremum.

16. The method of claim 1 , wherein:

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

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

17. The method of claim 16 , wherein the optical sensor comprises a photodiode, wherein receiving the return signal comprises receiving the first and second reflections concurrently at the photodiode.

18. The method of claim 1 , wherein:

the first optical output is transmit into the environment in a first direction; and

the second optical output is transmit into the environment in a second direction different from the first direction.

19. The method of claim 1 , further comprising, before selecting the set of PB-LCCs, selecting a sequence length, wherein the length of each PB-LCC of the set is equal to the sequence length.

20. The method of claim 19 , wherein the sequence length is selected based on a first set of desired performance metrics comprising at least one of: accuracy, range, resolution, or latency, the method further comprising:

based on the return signal, selecting a second sequence length different from the sequence length;

selecting a second set of PB-LCCs, the second set of PB-LCCs comprising a third PB-LCC and a fourth PB-LCC, wherein the length of each PB-LCC of the second set is equal to the second sequence length;

generating a third optical output representative of a third output signal, comprising modulating a third substantially continuous-wave carrier signal based on the third PB-LCC;

generating a fourth optical output representative of a fourth output signal, comprising modulating a fourth substantially continuous-wave carrier signal based on the fourth PB-LCC;

throughout a second time period after the time period, concurrently transmitting the third and fourth optical outputs into an environment;

at the optical sensor, receiving a second return signal, the second return signal comprising a reflection of at least one of the first or second optical output;

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

generating a third filtered sample, comprising filtering the second sample based on the third PB-LCC; and

generating a fourth filtered sample, comprising filtering the second sample based on the fourth PB-LCC.

21. The method of claim 1 , wherein:

the first PB-LCC comprises a first sub-sequence and a second sub-sequence;

the sample is selected from a first portion of the return signal associated with the first sub-sequence; and

filtering the sample based on the first PB-LCC comprises:

determining a second sample by selecting a second contiguous time window from a second portion of the return signal, the second portion associated with the second sub-sequence;

combining the first and second samples to generate a combined sample; and

applying a matched filter, associated with the first PB-LCC, to the combined sample.