Ladar Pulse Deconfliction Method

• US 20180239004A1
• Filed: 02/14/2018
• Published: 08/23/2018
• Est. Priority Date: 02/17/2017
• Status: Active Grant

• Current Assignee: AEye, Inc.
• Original Assignee: AEye, Inc.
• Inventors: Dussan, Luis Carlos, Steinhardt, Allan
• Granted Patent: US 10,379,205 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 2013/9316 combined with communication equipment with other vehicles or with base stations
• CPC Class Codes: G01S 7/006 using shared front-end circuitry, e.g. antennas G01S13/765, G01S13/825 take precedence
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/484 Transmitters
• CPC Class Codes: G01S 7/4861 Circuits for detection, sampling, integration or read-out
• CPC Class Codes: G01S 7/4865 Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak peak detection in noise, signal conditioning G01S7/487
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: G01S 7/4873 by deriving and controlling a threshold value
• CPC Class Codes: G01S 7/4876 by removing unwanted signals G01S7/495 takes precedence

Abstract

Disclosed herein are a number of example embodiments that employ controllable delays between successive ladar pulses in order to discriminate between “own” ladar pulse reflections and “interfering” ladar pulses reflections by a receiver. Example embodiments include designs where a sparse delay sum circuit is used at the receiver and where a funnel filter is used at the receiver. Also, disclosed are techniques for selecting codes to use for the controllable delays as well as techniques for identifying and tracking interfering ladar pulses and their corresponding delay codes. The use of a ladar system with pulse deconfliction is also disclosed as part of an optical data communication system.

Claims

1. A method comprising:

encoding a plurality of ladar pulses via a controllable delay between successive ladar pulses, wherein the controllable delay defines the encoding;

transmitting, by a ladar transmitter, the encoded ladar pulses;

receiving a signal, the received signal including the reflected encoded ladar pulses and noise; and

identifying the reflected encoded ladar pulses within the received signal based on the controllable delay.

2. The method of claim 1 wherein the noise in the received signal arises in part from interfering ladar pulses from other ladar transmitters.

3. The method of claim 2 wherein the identifying step comprises;

delaying the received signal by the controllable delay to generate a delayed signal;

summing the received signal with the delayed signal to generate a delay sum signal;

comparing the delay sum signal with a controllable threshold; and

determining whether the delay sum signal includes the reflected encoded ladar pulses based on the threshold comparison.

4. The method of claim 3 further comprising:

controllably adjusting the controllable threshold based on a statistical analysis of the received signal.

5. The method of claim 3 wherein the identifying step further comprises:

computing a first data value based on the delayed signal and a controllable value;

computing a second data value based on the received signal and the controllable value;

comparing the first data value with the received signal; and

comparing the second data value with the delayed signal; and

wherein the determining step comprises determining whether the delay sum signal includes the reflected encoded ladar pulses based on the threshold comparison, the comparison of the first data value with the received signal, and the comparison of the second data value with the delayed signal.

6. The method of claim 3 wherein the identifying step further comprises computing a smallest and largest value within the delayed samples and determining if the smallest/largest pair is inside or outside a defined region in two dimensional space.

7. The method of claim 5 further comprising:

controllably adjusting the controllable value based on the received signal and the delayed signal.

8. The method of claim 2 wherein the encoded ladar pulses comprise doublet pulses.

9. The method of claim 2 wherein the encoded ladar pulses comprise triplet pulses.

10. The method of claim 2 wherein the encoded ladar pulses comprise n-tuple pulses such that there are n−

1 controllable delays between n successive pulses as part of the encoding.

11. The method of claim 10 wherein a different controllable delay is employed between a plurality of the n successive ladar pulses.

12. The method of claim 2 further comprising repeatedly performing the method steps while the ladar transmitter is in motion.

13. The method of claim 12 further comprising:

determining whether the moving ladar transmitter has moved into a defined region; and

adjusting the controllable delay in response to a determination that the moving ladar transmitter has moved into the defined region.

14. The method of claim 13 wherein the defined region is a cellular region such that the controllable delay is adjusted as the ladar transmitter moves into new cellular regions.

15. The method of claim 2 further comprising:

selecting the controllable delay based on hashing.

16. The method of claim 2 wherein the encoding step comprises encoding the ladar pulses for a plurality of different ladar transmitters such that each of a plurality of the ladar transmitters employs a different controllable delay between successive ladar pulses.

17. The method of claim 16 further comprising each of a plurality of different ladar systems performing the identifying step non-cooperatively with the other ladar systems.

18. The method of claim 16 further comprising each of a plurality of different ladar systems performing the identifying step cooperatively with the other ladar systems.

19. The method of claim 18 further comprising:

a plurality of the ladar systems communicating with each other to share information for selecting different controllable delays among each other.

20. The method of claim 18 further comprising:

selecting the controllable delay based on delays that are posted to an electronic billboard.

21. The method of claim 16 wherein a plurality of the ladar transmitters are resident on automobiles, the method further comprising:

processing the noise in the received signal to generate data indicative of traffic conditions.

22. The method of claim 2 further comprising:

processing the received signals to extract the controllable delays corresponding to ladar pulses from other ladar transmitters; and

storing the extracted controllable delays for the other ladar transmitters.

23. The method of claim 1 further comprising:

generating a multi-static fused point cloud based on ladar pulses from a plurality of ladar systems.

24. The method of claim 1 wherein the identifying step is performed by a hardware circuit.

25. The method of claim 24 wherein the hardware circuit is resident on a field programmable gate array (FPGA).

26. The method of claim 1 wherein the transmitting step comprises spacing the encoded pulses in a sequence of shorter delays between pulse pairs and longer delays between the pulse pairs with the shorter delays.

27. The method of claim 26 wherein the receiving step comprises processing the reflected encoded ladar pulses such that a first set of reflections from the sequence are processed through a delay path and a second set of reflections from the sequence are processed through a non-delayed path.