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

Patent metadata

Field	Value
Publication number	US-11360215-B2
Application number	US-201816227770-A
Country	US
Kind code	B2
Filing date	Dec 20, 2018
Priority date	Dec 20, 2018
Publication date	Jun 14, 2022
Grant date	Jun 14, 2022

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 comprising:
a transmitter that is configured to emit a frequency-modulated lidar signal, wherein the frequency-modulated lidar signal includes a piecewise linear up-chirp, the piecewise linear up-chirp comprises:
a first portion having a first frequency rate of change; and
a second portion that is adjacent the first portion in the piecewise linear up-chirp, the second portion having a second frequency rate of change that is less than the first frequency rate of change, wherein the first portion has a first distance range assigned thereto and the second portion has a second distance range assigned thereto, the first distance range and the second distance range being non-overlapping; and

processing circuitry that is configured to:
determine, based upon the frequency-modulated lidar signal reflecting off of an object, whether the object is within the first distance range from the lidar system or the second distance range from the lidar system; and
compute a distance between the lidar system and the object based upon the frequency-modulated lidar signal, the processing circuitry configured to compute the distance with a first resolution when the distance is within the first distance range, the processing circuitry configured to compute the distance with a second resolution when the distance is within the second distance range, wherein the first resolution is higher than the second resolution.

2. The lidar system of claim 1 , wherein the first frequency rate of change is greater than the second frequency rate of change by a factor k.

3. The lidar system of claim 1 , further comprising:
a sensor; and
an analog to digital converter (ADC) that is operably coupled to the sensor and the processing circuitry, wherein the sensor is configured to output an analog sensor signal based upon a return reflection that impinges upon the sensor, wherein the return reflection is a portion of the frequency-modulated lidar signal that has reflected off of the object, the ADC is configured to output a digital signal that is representative of the analog sensor signal, and further wherein the processing circuitry is configured to:
perform a Fast Fourier Transform (FFT) over the digital signal to generate a frequency signal;
determine whether there is a single peak frequency in the frequency signal or multiple peak frequencies in the frequency signal; and
determine whether the object is within the first distance range from the lidar system or the second distance range from the lidar system based upon whether there is the single peak in the frequency signal or the multiple peaks in the frequency signal, respectively.

4. The lidar system of claim 3 , wherein the processing circuitry is further configured to:
when it is determined that there is a single peak frequency in the frequency signal, compute the distance with the second resolution based upon:
the second frequency rate of change of the first portion of the piecewise linear up-chirp; and
the single peak frequency.

5. The lidar system of claim 3 , wherein the processing circuitry is further configured to:
when it is determined that there are the multiple peak frequencies in the frequency signal, determine whether a difference between a first peak frequency and a second peak frequency in the multiple peak frequencies corresponds to a difference between the first frequency rate of change and the second frequency rate of change;
when it is determined that the difference between the first peak frequency and the second peak frequency corresponds to the difference between the first frequency rate of change and the second frequency rate of change, compute the distance with the first resolution based upon:
the first rate of change of the first portion of the piecewise linear up-chirp; and
the second peak frequency.

6. The lidar system of claim 1 , wherein the piecewise linear up-chirp comprises between two and five linear segments with differing frequency rates of change, and further wherein the frequency rates of change are successively decreasing in time.

7. The lidar system of claim 1 , wherein the processing circuitry is operably coupled to a computing system of an autonomous vehicle (AV), and further wherein the computing system of the AV controls at least one of a steering system, a braking system, or a propulsion system based upon the distance computed by the processing circuitry.

8. A lidar system comprising:
a transmitter that is configured to emit a frequency-modulated lidar signal, wherein the frequency-modulated lidar signal comprises a piecewise linear up-chirp, the piecewise linear up-chirp includes:
a first segment having a first slope; and
a second segment that is immediately adjacent to the first segment in the up-chirp, the second segment having a second slope that is less than the first slope, wherein the first segment has a first distance range assigned thereto and the second segment has a second distance range assigned thereto, the first distance segment and the second distance segment being non-overlapping;

a detector that is configured to detect a return signal, wherein the return signal is a reflection of the frequency-modulated lidar signal from an object; and
processing circuitry that is configured to:
based upon the return signal, determine whether the object is within the first distance range or the second distance range of the lidar system; and
compute a distance between the lidar system and the object based upon the return signal, wherein the processing circuitry is configured to compute the distance with a first resolution when the object is determined to be within the first distance range from the lidar system, and further wherein the processing circuitry is configured to compute the distance with a second resolution when the object is within the second distance range from the lidar system, the first resolution being more granular than the second resolution.

9. The lidar system of claim 8 , wherein the first slope equals the second slope multiplied by a constant k, wherein k is defined by a user.

10. The lidar system of claim 9 , wherein the transmitter comprises:
a laser source that is configured to output radiation;
control circuitry that is configured to compute a first voltage and a second voltage based upon k; and
a modulator that is operably coupled to the laser source and the control circuitry, wherein the modulator frequency-modulates the radiation output by the laser source using the first voltage and the second voltage to form the up-chirp in the frequency-modulated lidar signal.

11. The lidar system of claim 8 , further comprising:
an analog to digital converter (ADC) that is operably coupled to the detector and the processing circuitry, wherein the detector is configured to output an analog sensor signal based upon the return signal, the ADC is configured to output a digital signal that is representative of the analog sensor signal, and further wherein the processing circuitry is configured to:
perform a Fast Fourier Transform (FFT) over the digital signal to generate a frequency signal;
determine whether there is a single peak frequency in the frequency signal or multiple peak frequencies in the frequency signal; and
determine whether the object is within the first distance range or the second distance range of the lidar system based upon whether there is the single peak in the frequency signal or the multiple peaks in the frequency signal, respectively.

12. The lidar system of claim 11 , wherein the processing circuitry is further configured to:
when it is determined that there is the single peak frequency in the frequency signal,

Assignees

• Gm Cruise Holdings Llc

Inventors

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

Classifications

• B60W2710/20

  Steering systems · CPC title

• B60W30/18

  Propelling the vehicle · CPC title

• B60W2710/06

  Combustion engines, Gas turbines · CPC title

• B60W2710/18

  Braking system · CPC title

• G01S7/4808

  Evaluating distance, position or velocity data · CPC title