Processing temporal segments of laser chirps and examples of use in FMCW LiDAR methods and apparatuses
Examples of FMCW laser radar systems and methods described herein may segment the processing of a broader bandwidth frequency chirp into multiple shorter-duration (e.g., lower bandwidth) frequency chirps. This segmentation may have the benefits in some examples of improving the measurement duty cycle and range resolution, and/or allowing for more flexible processing, and/or enabling improved detection of more distant objects.
1. A method comprising:
producing an interference signal from a frequency-modulated continuous wave (FMCW) laser radar system, the interference signal corresponding to a laser chirp over a chirp bandwidth;
processing multiple temporal segments of the interference signal, each of the multiple temporal segments corresponding to a respective segmented bandwidth, each of the respective segmented bandwidths being less than the chirp bandwidth; and
determining a distance to at least a portion of an object based on the processing, wherein an update rate of the FMCW laser radar system is faster than the inverse of the laser chirp duration.
2. The method of claim 1 , wherein producing the interference signal comprises:
directing a transmit portion of a laser beam corresponding to the laser chirp toward the object; and
combining a reflected portion of the transmit portion of the laser beam with a local oscillator portion of the laser beam.
3. The method of claim 1 , wherein said processing comprises combining results from processing the multiple temporal segments.
4. The method of claim 3 , wherein said combining comprises averaging.
5. The method of claim 4 , wherein said averaging comprises incoherent averaging.
6. The method of claim 1 , wherein the interference signal comprises a first interference signal, the first interference signal corresponding to a first laser chirp comprising a first set of multiple temporal segments, the method further comprising producing a second interference signal from the frequency-modulated continuous wave (FMCW) laser radar system, the second interference signal corresponding to a second laser chirp comprising a second set of multiple temporal segments; and
processing at least one of the first set of multiple temporal segments with at least one of the second set of multiple temporal segments to determine the distance.
7. The method of claim 6 , wherein the at least one of the first set of multiple temporal segments and the at least one of the second set of multiple temporal segments overlap temporally.
8. The method of claim 6 , wherein the at least one of the first set of multiple temporal segments and the at least one of the second set of multiple temporal segments correspond to same optical frequencies.
9. The method of claim 6 , wherein the first and second sets of multiple temporal segments correspond to interference signals from different laser beams.
10. The method of claim 6 , wherein said processing at least one of the first set of multiple temporal segments with at least one of the second set of multiple temporal segments at least partially compensates for Doppler noise, speckle noise, or combinations thereof.
11. The method of claim 6 , wherein the first and second laser chirps are in opposite directions.
12. A method comprising:
producing an interference signal from a frequency-modulated continuous wave (FMCW) laser radar system, the interference signal corresponding to a laser chirp over a chirp bandwidth, wherein the interference signal comprises a first interference signal, the first interference signal corresponding to a first laser chirp comprising a first set of multiple temporal segments;
producing a second interference signal from the frequency-modulated continuous wave (FMCW) laser radar system, the second interference signal corresponding to a second laser chirp comprising a second set of multiple temporal segments;
processing multiple temporal segments of the interference signal, each of the multiple temporal segments corresponding to a respective segmented bandwidth, each of the respective segmented bandwidths being less than the chirp bandwidth;
determining a distance to at least a portion of an object based on the processing; and
processing at least one of the first set of multiple temporal segments with at least one of the second set of multiple temporal segments to determine the distance, wherein the first and second sets of multiple temporal segments correspond to an interference signal from a same laser beam.
13. A system comprising:
at least one laser source configured to provide a chirped laser beam to be directed toward, and at least partially reflected by, an object to provide a reflected laser beam, wherein the at least one laser source is configured to provide the chirped laser beam chirped over a chirp bandwidth;
a detector configured to combine a local oscillator portion of the chirped laser beam and the reflected laser beam to provide an interference signal; and
at least one processor configured to process multiple temporal segments of the interference signal, each of the multiple temporal segments corresponding to a respective segmented bandwidth, each of the respective segmented bandwidths less than the chirp bandwidth, and determine a distance to at least a portion of the object, wherein the at least one processor is configured to determine the distance to the at least a portion of the object at an update rate, and wherein the update rate is greater than the inverse of the duration of the laser chirp.
14. The system of claim 13 , wherein the at least one laser source comprises a first laser source configured to provide a first laser chirp comprising a first set of temporal segments, and wherein the at least one laser source additionally comprises a second laser source configured to provide a second laser chirp comprising a second set of temporal segments.
15. The system of claim 14 , wherein the first and second sets of temporal segments do not overlap temporally.
16. The system of claim 14 , wherein at least one of the first set of temporal segments overlaps temporally with at least one of the second set of temporal segments.
17. The system of claim 13 , wherein the at least one processor is configured to combine results from processing multiple temporal segments.
18. The system of claim 17 , wherein the at least one processor is configured to average results from processing multiple temporal segments.
19. A system comprising:
at least one laser source configured to provide a chirped laser beam to be directed toward, and at least partially reflected by, an object to provide a reflected user beam, wherein the at least one laser source is configured to provide the chirped laser beam chirped over a chirp bandwidth;
a detector configured to combine a local oscillator portion of the chirped laser beam and the reflected laser beam to provide an interference signal; and
at least one processor configured to process multiple temporal segments of the interference signal, each of the multiple temporal segments corresponding to a respective segmented bandwidth, each of the respective segmented bandwidths less than the chirp bandwidth, and determine a distance to at least a portion of the object wherein the at least one processor is configured to combine results from processing multiple temporal segments, wherein the at least one processor is configured to determine a plurality of initial distances to the at least a portion of the object, wherein each of the plurality of initial distances is based on a respective one of the multiple temporal segments, and wherein the at least one processor is configured to determine the distance to the at least at least a portion of the object based on combining the plurality of initial distances.