Ladar Receiver Range Measurement using Distinct Optical Path for Reference Light

• US 20170242109A1
• Filed: 02/10/2017
• Published: 08/24/2017
• Est. Priority Date: 02/18/2016
• Status: Active Grant

• Current Assignee: AEye, Inc.
• Original Assignee: AEye, Inc.
• Inventors: Dussan, Luis Carlos, Steinhardt, Allan, Cook, David
• Granted Patent: US 10,782,393 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• 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 17/26 wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4814 of transmitters alone
• CPC Class Codes: G01S 7/4815 using multiple transmitters
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates
• 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 7/4876 by removing unwanted signals G01S7/495 takes precedence
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

Disclosed herein are various embodiment of an adaptive ladar receiver and associated method whereby the active pixels in a photodetector array used for reception of ladar pulse returns can be adaptively controlled based at least in part on where the ladar pulses were targeted. Additional embodiments disclose improved imaging optics for use by the receiver and further adaptive control techniques for selecting which pixels of the photodetector array are used for sensing incident light.

Claims

1. A method comprising:

transmitting a ladar pulse toward a targeted range point in a field of view, the transmitted ladar pulse exhibiting a pulse shape;

transmitting an optical pulse toward a light sensor via a first optical path, wherein the transmitted optical pulse exhibits the same pulse shape as the transmitted ladar pulse;

sensing light via the light sensor, wherein the sensed light includes (1) light corresponding to a reflection of the transmitted ladar pulse that travels to the light sensor via a second optical path and (2) light corresponding to the transmitted optical pulse that travels to the light sensor via the first optical path;

converting the sensed light into an electrical signal;

digitizing the electrical signal into a plurality of samples;

applying a delay to the samples to generate a plurality of delayed samples;

correlating the samples against the delayed samples to find an alignment between the samples and delayed samples that produces a maximal output; and

determining a timing relationship between the optical pulse and the ladar pulse based on the correlating.

2. The method of claim 1 further comprising:

computing range information with respect to the targeted range point based on the determined timing relationship.

3. The method of claim 1 wherein the light corresponding to ladar pulse reflection and the light corresponding to the optical pulse are separated by a time delay during their reception by the light sensor;

and

wherein the correlating step comprises shifting, sample-by-sample, the samples against the delayed samples such that the maximal output corresponds to a number of sample shifts, wherein the number of sample shifts is indicative of the time delay.

4. The method of claim 1 wherein the light sensor comprises a photodetector array, the photodetector array comprising a plurality of addressable pixels.

5. The method of claim 4 further comprising:

selecting which of the pixels are activated for sensing the light based on a location of the targeted range point in a scan area for a ladar transmitter that transmits the ladar pulse.

6. The method of claim 1 further comprising:

interpolating the delayed samples; and

wherein the correlating step comprises correlating the samples against the interpolated delayed samples to find the alignment that produces the maximal output.

7. The method of claim 1 wherein the first optical path is a direct optical path between (1) a transmitter that transmits the ladar pulses and the optical pulse, and (2) the light sensor.

8. The method of claim 1 wherein the optical pulse and the ladar pulse are the same pulse.

9. The method of claim 1 further comprising:

repeating the method steps a plurality of times with respect to a plurality of ladar pulses transmitted by a ladar transmitter toward a plurality of range points via compressive sensing.

10. An apparatus comprising:

a light sensor configured to sense incident light, wherein the sensed light includes (1) light corresponding to a reflection of a ladar pulse and (2) light corresponding to an optical pulse that is distinct from the ladar pulse, wherein the ladar pulse and the optical pulse are identical pulses; and

a circuit configured to (1) convert a signal corresponding to the sensed light into a plurality of digital samples, (2) apply a delay to the samples to generate a plurality of delayed samples, (3) correlate the samples against the delayed samples to find an alignment between the samples and delayed samples that produces a maximal output, and (4) determine a timing relationship between the optical pulse and the ladar pulse based on the correlation.

11. The apparatus of claim 10 wherein the circuit is further configured to compute range information with respect to a range point targeted by the ladar pulse based on the determined timing relationship.

12. The apparatus of claim 10 wherein the light corresponding to ladar pulse reflection and the light corresponding to the optical pulse are separated by a time delay during their reception by the light sensor;

and

wherein the circuit is further configured to perform the correlation by shifting, sample-by-sample, the samples against the delayed samples such that the maximal output corresponds to a number of sample shifts, wherein the number of sample shifts is indicative of the time delay.

13. The apparatus of claim 10 wherein the light sensor comprises a photodetector array, the photodetector array comprising a plurality of addressable pixels.

14. The method of claim 13 wherein the circuit is further configured to select which of the pixels are activated for sensing the light based on a location, in a scan area for a ladar transmitter that transmits the ladar pulse, of the a range point targeted by the ladar pulse.

15. The apparatus of claim 10 wherein the circuit is further configured to (1) interpolate the delayed samples, and (2) perform the correlation by correlating the samples against the interpolated delayed samples to find the alignment that produces the maximal output.

16. The apparatus of claim 10 further comprising:

a ladar transmitter, wherein the ladar transmitter is configured to (1) transmit the ladar pulse toward a targeted range point, and (2) transmit the optical pulse toward the light sensor

17. The apparatus of claim 15 wherein the ladar transmitter is further configured to target a plurality of range points with transmitted ladar pulses via compressive sensing.

18. The apparatus of claim 16 wherein the transmitter is configured to transmit the optical pulse to the light sensor via an optical path that is distinct from an optical path traveled by the ladar pulse to the range point and back to the light sensor as the ladar pulse reflection.

19. An apparatus comprising:

a light sensor; and

an analog-to-digital converter (ADC) in communication with the light sensor, the ADC configured to convert an electrical signal sensed by the light sensor into a plurality of digital samples, wherein the electrical signal is representative of light sensed by the light sensor; and

a match filter that is configured to process the samples to detect a time delay between a plurality of pulses that are represented within the samples, wherein the pulses exhibit a common shape.

20. The apparatus of claim 19 further comprising:

a ladar transmitter that is configured to (1) transmit a ladar pulse toward a targeted range point via a first optical path, and (2) transmit an optical pulse toward the light sensor via a second optical path, wherein the ladar pulse and the optical pulse share the common pulse shape;

wherein the light sensor is configured to sense incident light that includes (1) light corresponding to a reflection of the transmitted ladar pulse and (2) light corresponding to the transmitted optical pulse; and

wherein the match filter is configured to detect the time delay between the sensed ladar pulse reflection and the sensed optical pulse.