Lidar system that is configured to compute ranges with differing range resolutions

Patent metadata

Field	Value
Publication number	US-11774591-B2
Application number	US-202117561058-A
Country	US
Kind code	B2
Filing date	Dec 23, 2021
Priority date	Dec 20, 2018
Publication date	Oct 3, 2023
Grant date	Oct 3, 2023

Abstract

A lidar system is described herein. The lidar system includes a transmitter that is configured to emit a frequency-modulated lidar signal. The lidar system further includes processing circuitry that is configured to compute a distance between the lidar system and an object based upon the frequency-modulated lidar signal, the processing circuitry configured to compute the distance with a first resolution when the distance is at or beneath a predefined threshold, the processing circuitry configured to compute the distance with a second resolution when the distance is above the predefined threshold, wherein the first resolution is different from the second resolution.

First claim

What is claimed is:

1. A lidar system that comprises circuitry, wherein the circuitry is configured to perform acts comprising:
detecting a lidar return signal, wherein the lidar return signal is a reflection of a lidar signal off of an object, and further wherein the lidar signal is emitted by a lidar system;
computing a number of beat frequencies that correspond to the lidar return signal based upon the lidar return signal and a local oscillator;
based upon the number of beat frequencies, determining whether the object is within a first distance range from the lidar system or a second distance range from the lidar system, wherein the first distance range and the second distance range are non-overlapping;
when it is determined that the object is within the first distance range, computing a distance between the object and the lidar system with a first resolution; and
when it is determined that the object is within the second distance range, computing the distance between the object and the lidar system with a second resolution, wherein the first resolution is higher than the second resolution.

2. The lidar system of claim 1 being a frequency modulated continuous wave (FMCW) lidar system.

3. The lidar system of claim 1 , the acts further comprising:
transmitting the lidar signal, wherein the lidar signal includes a pulse that comprises an upchirp and a downchirp, and further wherein the upchirp comprises:
a first segment that has a first frequency rate of change; and
a second segment that immediately follows the first segment, the second segment has a second frequency rate of change that is different from the first frequency rate of change, and further wherein the number of beat frequencies that correspond to the lidar return signal is based upon a mixing of the pulse of the lidar signal with the local oscillator.

4. The lidar system of claim 3 , wherein the local oscillator includes a second pulse that comprises a second upchirp and a second downchirp, wherein the second upchirp comprises:
a third segment that has the first frequency rate of change; and
a fourth segment that immediately follows the third segment, the fourth segment has the second frequency rate of change, and further wherein the number of beat frequencies that correspond to the lidar return signal is based upon a mixing of the pulse of the lidar signal with the second pulse of the local oscillator.

5. The lidar system of claim 4 , wherein the downchirp comprises:
a fifth segment that has a third frequency rate of change; and
a sixth segment that immediately follows the fifth segment, the sixth segment has a fourth frequency rate of change that is different from the third frequency rate of change, and further wherein the second downchirp of the local oscillator comprises:
a seventh segment that has the third frequency rate of change; and
an eighth segment that immediately follows the seventh segment, the eighth segment has the fourth frequency rate of change.

6. The lidar system of claim 5 , wherein an absolute value of the first frequency rate of change is greater than an absolute value of the second frequency rate of change.

7. The lidar system of claim 5 , wherein an absolute value of the third frequency rate of change is greater than an absolute value of the fourth frequency rate of change.

8. The lidar system of claim 3 , wherein the pulse has a length in time of T, and further wherein each of the upchirp and the downchirp have a length in time of T/2.

9. The lidar system of claim 3 , wherein the first distance range is closer to the lidar system than the second distance range, and further wherein the first distance range corresponds to the first segment and the second distance range corresponds to the second segment.

10. The lidar system of claim 1 included in a sensor suite of an autonomous vehicle, wherein the autonomous vehicle autonomously navigates about a region based upon the computed distance.

11. A method performed by a lidar system, the method comprising:
transmitting a lidar signal into an environment of the lidar system, wherein the lidar signal reflects off of an object that is at a distance from the lidar system;
detecting a return signal based upon the lidar signal reflecting off of the object;
mixing the return signal with a local oscillator to form a mixed signal;
computing a number of beat frequencies in the mixed signal;
determining a distance range corresponding to the object, wherein:
when the number of beat frequencies is a first number, determining that the distance of the object from the lidar system is within a first distance range; and
when the number of beat frequencies is a second number, determining that the distance of the object from the lidar system is within a second distance range, wherein the first distance range and the second distance range are non-overlapping.

12. The method of claim 11 , further comprising:
subsequent to determining the distance range corresponding to the object, computing the distance of the object from the lidar system, wherein:
the distance is computed with a first resolution when the object is within the first distance range; and
the distance is computed with a second resolution when the object is within the second distance range, wherein the first resolution is different from the second resolution.

13. The method of claim 12 , wherein the first distance range is closer to the lidar system than the second distance range, and further wherein the first resolution is higher than the second resolution.

14. The method of claim 11 , wherein the lidar signal includes a pulse that comprises a piecewise linear upchirp and a piecewise linear downchirp, and further wherein the local oscillator includes a second pulse that comprises a second piecewise linear upchirp and a second piecewise linear downchirp.

15. The method of claim 14 , wherein the piecewise linear upchirp comprises:
a first segment that has a first frequency rate of change; and
a second segment that immediately follows the first segment, the second segment has a second frequency rate of change that is different from the first frequency rate of change, and further wherein the number of beat frequencies that correspond to the lidar return signal is based upon a mixing of the pulse with the second pulse.

16. The method of claim 15 , wherein the second piecewise linear upchirp comprises:
a third segment that has the first frequency rate of change; and
a fourth segment that immediately follows the third segment, the fourth segment has the second frequency rate of change, and further wherein computing of the number of beat frequencies is based upon a mixing of the pulse of the lidar signal with the second pulse of the local oscillator.

17. The method of claim 11 , further comprising:
computing the distance from the lidar system to the object with a resolution that depends upon the determined distance range; and
transmitting the computed distance to a computing system of an autonomous vehicle, wherein the autonomous vehicle autonomously navigates on a roadway based upon the computed distance from the lidar system to the object.

18. A method performed by a lidar system, the method comprising:
detecting a lidar return signal, wherein the lidar return signal is a reflection of a lidar signal off of an object, and further wherein the lidar signal is emitted by a lidar system;
computing a number of beat frequencies that correspond to the lidar return signal based upon the lidar return signal and a local oscillator;
based upon the number

Assignees

• Gm Cruise Holdings Llc

Inventors

• Singer Scott
• Maleki Lutfollah
• Standridge Alexander Charles
• Chakrabarty Ayan

Classifications

• G01S17/34 Primary

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