Low latency intra-frame motion estimation based on clusters of ladar pulses

• US 10,641,900 B2
• Filed: 08/21/2018
• Issued: 05/05/2020
• Est. Priority Date: 09/15/2017
• Status: Active Grant

• Current Assignee: AEye, Inc.
• Original Assignee: AEye, Inc.
• Inventors: Dussan, Luis Carlos, Steinhardt, Allan, Benscoter, Joel David, Greene, Jordan Spencer
• Primary Examiner(s): Ratcliffe, Luke D
• Application Number:
  US16/106,406
• Publication Number:
  US 20190086514A1
• Time in Patent Office: 623 Days
• 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 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• 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 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G01S 7/4814 of transmitters alone
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/484 Transmitters
• CPC Class Codes: G01S 7/4861 Circuits for detection, sampling, integration or read-out
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0085 for use with both a detector and a source , e.g. in a transceiver, G02B19/009, G02B19/0095 take precedence
• CPC Class Codes: G02B 26/108 having one or more prisms as scanning elements

Abstract

A ladar system can estimate intra-frame motion for an object within a field of view of the ladar system using a tight cluster of ladar pulses. For example, ladar pulses in a cluster can be spaced apart but overlapping with at least one of the other ladar pulses in that cluster at a specified distance in the field of view. A ladar receiver can then process the reflections from the cluster to computer intra-frame motion data, such as intra-frame velocity and intra-frame acceleration for an object.

Claims

1. An apparatus comprising:

a ladar transmitter configured to transmit a cluster of ladar pulses within a ladar frame toward a target within a field of view, wherein each of a plurality of the ladar pulses in the cluster is temporally and spatially spaced apart relative to the other ladar pulses in the cluster but spatially overlapping with at least one of the other ladar pulses in the cluster at a specified distance in the field of view;

a ladar receiver configured to receive reflections of the transmitted cluster of ladar pulses; and

a circuit configured to (1) process data representative of the received reflections and (2) compute intra-frame motion data for the target based on the processed data.

2. The apparatus of claim 1 wherein the intra-frame motion data comprises intra-frame velocity data for the target.

3. The apparatus of any claim 1 wherein the intra-frame motion data comprises intra-frame acceleration data for the target.

4. The apparatus of claim 1 wherein the ladar transmitter comprises:

a plurality of scanable mirrors; and

a beam scanner controller configured to aim the ladar transmitter toward the target via control over the scanable mirrors.

5. The apparatus of claim 4 wherein the circuit comprises a processor, the processor configured to detect the target based on at least one of ladar data and/or image data.

6. The apparatus of claim 5 wherein the processor is further configured to:

determine a first coordinate along a first axis and a second coordinate along a second axis in the field of view for the detected target, wherein the first and second axes are orthogonal to each other;

define a first ladar pulse and a second ladar pulse for the cluster, wherein the first and second ladar pulses are both targeted to the first coordinate along the first axis but to different coordinates along the second axis such that the first and second ladar pulses are overlapping with each other at the specified distance in the field of view; and

process reflection data for the first and second ladar pulses to compute a position for the detected target along the second axis.

7. The apparatus of claim 6 wherein the processor is further configured to:

define a third ladar pulse for the cluster, wherein the third ladar pulse is targeted to the first coordinate along the first axis and the computed position along the second axis; and

define a fourth ladar pulse for the cluster, wherein the fourth ladar pulse is targeted to a third coordinate along the first axis and the computed position along the second axis, wherein the first and third coordinates along the first axis are different but where at least one of the third and fourth ladar pulses encompasses the detected target; and

process reflection data for the third and fourth ladar pulses to compute the intra-frame motion data for the detected target.

8. The apparatus of claim 7 wherein the processor is configured to:

compute range and intensity data for the reflections of the third and fourth ladar pulses based on the processed reflection data;

compute a cross-range and range centroid of the detected target based on the computed range and intensity data; and

compute the intra-frame motion data for the detected target based on changes over time in the computed centroids.

9. The apparatus of claim 6 wherein the first axis is azimuth, and wherein the second axis is elevation.

10. The apparatus of claim 4 wherein the ladar transmitter is further configured to selectively target range points in the field of view based on compressive sensing.

11. The apparatus of claim 1 wherein the circuit is further configured to:

controllably select of plurality of ladar pulses for transmission during a subsequent frame based on the computed intra-frame motion data for the target.

12. The apparatus of claim 1 further comprising:

a camera that is co-bore sited with the ladar receiver, the camera configured to generate image data corresponding to a field of view for the ladar receiver; and

wherein the circuit comprises a processor, the processor configured to detect the target based on the generated image data.

13. The apparatus of claim 1 wherein the ladar pulses in the cluster have beam profiles that spatially overlap at an offset with respect to a beam profile of at least one of the other ladar pulses in the cluster at the specified distance in the field of view.

14. The apparatus of any claim 2 wherein the intra-frame motion data further comprises intra-frame acceleration data for the target.

15. A method comprising:

transmitting a cluster of ladar pulses within a ladar frame toward a target within a field of view, wherein each of a plurality of the ladar pulses in the cluster is temporally and spatially spaced apart relative to the other ladar pulses in the cluster but spatially overlapping with at least one of the other ladar pulses in the cluster at a specified distance in the field of view;

receiving reflections of the transmitted cluster of ladar pulses;

processing data representative of the received reflections; and

computing intra-frame motion data for the target based on the processed data.

16. The method of claim 15 wherein the intra-frame motion data comprises intra-frame velocity data for the target.

17. The method of claim 15 wherein the intra-frame motion data comprises intra-frame acceleration data for the target.

18. The method of claim 15 further comprising:

scanning a plurality of mirrors; and

wherein the transmitting step comprises aiming and transmitting the ladar pulses toward the target via the scanning mirrors.

19. The method of claim 18 further comprising:

a processor detecting the target based on at least one of ladar data and/or image data.

20. The method of claim 19 further comprising:

a processor determining a first coordinate along a first axis and a second coordinate along a second axis in the field of view for the detected target, wherein the first and second axes are orthogonal to each other;

a processor defining a first ladar pulse and a second ladar pulse for the cluster, wherein the first and second ladar pulses are both targeted to the first coordinate along the first axis but to different coordinates along the second axis such that the first and second ladar pulses are overlapping with each other at the specified distance in the field of view; and

a processor processing reflection data for the first and second ladar pulses to compute a position for the detected target along the second axis.

21. The method of claim 20 further comprising:

a processor defining a third ladar pulse for the cluster, wherein the third ladar pulse is targeted to the first coordinate along the first axis and the computed position along the second axis; and

a processor defining a fourth ladar pulse for the cluster, wherein the fourth ladar pulse is targeted to a third coordinate along the first axis and the computed position along the second axis, wherein the first and third coordinates along the first axis are different but where at least one of the third and fourth ladar pulses encompasses the detected target; and

a processor processing reflection data for the third and fourth ladar pulses to compute the intra-frame motion data for the detected target.

22. The method of claim 21 further comprising:

a processor computing range and intensity data for the reflections of the third and fourth ladar pulses based on the processed reflection data;

a processor computing a cross-range and range centroid of the detected target based on the computed range and intensity data; and

a processor computing the intra-frame motion data for the detected target based on changes over time in the computed centroids.

23. The method of claim 20 wherein the first axis is azimuth, and wherein the second axis is elevation.

24. The method of claim 15 further comprising:

controllably selecting of plurality of ladar pulses for transmission during a subsequent frame based on the computed intra-frame motion data for the target.

25. The method of claim 15 further comprising:

a camera that is co-bore sited with the ladar receiver generating image data corresponding to a field of view for the ladar receiver; and

detecting the target based on the generated image data.

26. The method of claim 15 further comprising:

selectively targeting a plurality of the ladar pulses toward a plurality of range points in the field of view based on compressive sensing.

27. The method of claim 15 wherein the ladar pulses in the cluster have beam profiles that spatially overlap at an offset with respect to a beam profile of at least one of the other ladar pulses in the cluster at the specified distance in the field of view.

28. The method of claim 16 wherein the intra-frame motion data further comprises intra-frame acceleration data for the target.