Method to improve probability of detection in dynamic scenarios in coherent LIDAR systems

1. A method of compensating for phase impairments in a light detection and ranging (LIDAR) system comprising:

transmitting a first optical beam towards a target;

receiving, based on the first optical beam, a second optical beam from the target to produce a return signal;

generating a digitally-sampled target signal using a local oscillator (LO) beam, a first photo-detector, and the return signal;

compensating for ego-velocity and target velocity in the digitally-sampled target signal based on an estimated ego-velocity and an estimated target velocity to produce a compensated digitally-sampled target signal; and

performing a phase impairment correction on the compensated digitally-sampled target signal for transmission to a point cloud.

2. The method of claim 1 , further comprising:

determining the ego-velocity of the LIDAR system, wherein the ego-velocity is a velocity of the LIDAR system calculated based on neighboring objects measured using one or more motion sensors.

3. The method of claim 1 , wherein compensating for the ego-velocity and target velocity in the digitally-sampled target signal further comprises:

applying a first frequency shift to the digitally-sampled target signal, the first frequency shift being a function of an ego-velocity of the LIDAR system; and

applying a second frequency shift to the digitally-sampled target signal, the second frequency shift being a conjugate of the first frequency shift.

4. The method of claim 1 , further comprising:

generating a digitally-sampled reference signal using a reference beam transmitted through a fiber delay device and a second photo-detector; and

wherein performing the phase impairment correction on the digitally-sampled target signal comprises correcting for phase impairments introduced into the digitally-sampled target signal by the LO beam and by the return signal.

5. The method of claim 1 , further comprising:

determining a velocity of neighboring points in a vicinity of the target; and

generating the estimated target velocity based on the velocity of neighboring points.

6. The method of claim 5 , wherein determining the velocity of neighboring points comprises:

running a standard corrector on all neighboring points; and

estimating a statistic of the velocity of neighboring points.

7. The method of claim 1 , further comprising:

determining a velocity of previous points of the target within a point cloud; and

generating the estimated target velocity based on the velocity of previous points.

8. The method of claim 7 , wherein determining a velocity of previous points of the target within the point cloud comprises determining a velocity of an immediately preceding point in a same scan line, determining a velocity of points from previous scan lines, or determining a velocity of points from previous scan-frames.

9. A light detection and ranging (LIDAR) system comprising:

an optical beam source to transmit a first optical beam to a target;

a first photo detector to receive a return signal from the target and a local oscillator (LO) beam and generate a digitally-sampled target signal;

a fiber delay device having a known length and coupled to the optical beam source;

a second detector coupled to the fiber delay device to generate a digitally-sampled reference signal using a reference beam transmitted through the fiber delay device;

at least two frequency shifters to compensate for ego-velocity and target velocity in the digitally-sampled target signal based on an estimated ego-velocity and estimated target velocity; and

a deskew filter to perform a phase impairment correction on the digitally-sampled target signal.

10. The system of claim 9 , wherein the ego-velocity is a velocity of the LIDAR system with respect to neighboring objects measured using one or more motion sensors.

11. The system of claim 9 , wherein the at least two frequency shifters include:

a first frequency shifter to apply a first frequency shift to the digitally-sampled target signal, the first frequency shift being a function of an ego-velocity of the LIDAR system; and

a second frequency shifter to apply a second frequency shift to the digitally-sampled target signal, the second frequency shift being a conjugate of the first frequency shift.

12. The system of claim 9 , wherein the phase impairment correction on the digitally-sampled target signal corrects for phase impairments introduced into the digitally-sampled target signal by the LO beam and by the return signal.

13. The system of claim 12 , wherein the LIDAR system is further configured to determine the estimated target velocity based on a velocity of neighboring points in a vicinity of the target.

14. The system of claim 13 , wherein the LIDAR system determines the velocity of neighboring points by running a standard corrector on all neighboring points; and estimating a statistic of the velocity of neighboring points.

15. The system of claim 12 , wherein the LIDAR system is further configured to determine the estimated target velocity based on a velocity of previous points of the target within a point cloud.

16. The system of claim 15 , wherein the LIDAR system determines the velocity of previous points by determining a velocity of an immediately preceding point in a same scan line, determining a velocity of points from previous scan lines, or determining a velocity of points from previous scan-frames.

17. A method of compensating for phase impairments in a light detection and ranging (LIDAR) system comprising:

transmitting a first optical beam to a target from the LIDAR system;

receiving, at the LIDAR system, a return signal from the target at a first photo detector;

generating a digitally-sampled reference signal using a reference beam transmitted through a fiber delay device and a second photo-detector;

estimating one or more phase impairments in the LiDAR system using the digitally-sampled reference signal to produce one or more estimated phase impairments;

applying a first frequency shift to the digitally-sampled target signal, the first frequency shift being a function of the ego-velocity of the LIDAR system and an estimated target velocity;

adjusting for phase impairments in the digitally-sampled target signal for transmission to a point cloud using a deskew filter; and

applying a second frequency shift to the digitally-sampled target signal, the second frequency shift being a conjugate of the first frequency shift.

18. The method of claim 17 , wherein adjusting for phase impairments in the digitally-sampled target signal comprises correcting for phase impairments introduced into the digitally-sampled target signal by the LO beam and by the return signal.

19. The method of claim 18 , further comprising:

determining a velocity of neighboring points in a vicinity of the target; and

generating the estimated target velocity based on the velocity of neighboring points.

20. The method of claim 17 , further comprising:

determining a velocity of previous points of the target within a point cloud; and

generating the estimated target velocity based on the velocity of previous points.