Adaptive ladar receiver

Patent metadata

Field	Value
Publication number	US-10754015-B2
Application number	US-201715430192-A
Country	US
Kind code	B2
Filing date	Feb 10, 2017
Priority date	Feb 18, 2016
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

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.

First claim

What is claimed is:

1. A ladar receiver apparatus comprising:
an array comprising a plurality of light sensors, each light sensor configured to sense light that is indicative of a plurality of ladar pulses reflected from a plurality of range points and generate a signal indicative of the sensed light; and
a circuit in communication with the array, the circuit configured to (1) process data indicative of a plurality of locations in a field of view that are targeted with the ladar pulses, and (2) based on the processed location data, selectively define a plurality of subsets of the light sensors for read out at a given time to produce a signal representative of the sensed light, the produced signal for use in computing range information with respect to the range points, wherein the processed location data represents locations of range points in the field of view targeted by a scanning ladar transmitter that transmits the ladar pulses toward the targeted range points;
wherein the circuit comprises:
a signal processing circuit;
a multiplexer in communication with the array and the signal processing circuit, wherein the multiplexer is configured to selectively connect each defined subset of the light sensors with the signal processing circuit in response to a control signal such that the multiplexer passes the signal generated by each selectively connected light sensor to the signal processing circuit, wherein the control signal is derived from the processed location data; and
a control circuit in communication with the multiplexer, the control circuit configured to generate the control signal from the processed location data such that the control signal selects subsets of light sensors within the array based on the locations of the targeted range points in the field of view; and

wherein the signal processing circuit is configured to amplify and convert the provided signals into a plurality of digital samples for processing to compute the range information with respect to the range points.

2. The apparatus of claim 1 wherein the processed location data comprises a shot list for the scanning ladar transmitter, and wherein the control circuit is further configured to generate the control signal such that the control signal selects subsets of light sensors within the array in a sequence that follows the locations for the targeted range points defined by the shot list.

3. The apparatus of claim 2 wherein the shot list selectively targets a subset of range points within the field of view.

4. The apparatus of claim 1 wherein the circuit further comprises:
a feedback circuit that provides a plurality of feedback signals to the light sensors for adjusting outputs from the light sensors.

5. The apparatus of claim 4 wherein the feedback circuit comprises a plurality of amplifiers between the light sensors and the multiplexer that amplify the outputs from the light sensors in a controlled feedback loop.

6. The apparatus of claim 5 further comprising a gain controller configured to control the amplifiers to produce a feedback gain that increases a signal to noise ratio for the outputs from the light sensors.

7. The apparatus of claim 5 wherein the feedback circuit is configured as a matching network feedback loop.

8. The apparatus of claim 4 wherein the ladar pulses comprise a plurality of ladar pulses that exhibit a Gaussian pulse shape.

9. The apparatus of claim 1 wherein the signal processing circuit includes a single channel for the signal passed by the multiplexer.

10. The apparatus of claim 1 wherein the signal processing circuit includes a plurality of channels for the signal passed by the multiplexer, and wherein the signal processing circuit is configured to reduce a noise component of the signal passed by the multiplexer based on signals present in the plurality of channels.

11. The apparatus of claim 10 wherein the signal processing circuit comprises a coherent combination circuit for the plurality of channels that includes a filter for reducing a spatially directional noise component of the signal passed by the multiplexer.

12. The apparatus of claim 1 wherein each of a plurality of the subsets comprises a plurality of the light sensors, and wherein circuits are positioned to combine signals from a plurality of light sensors to each of a plurality of multiplexer input lines to thereby define composite pixels for readout to the signal processing circuit.

13. The apparatus of claim 1 wherein the signal processing circuit comprises an amplifier configured to amplify the provided signals.

14. The apparatus of claim 13 wherein the signal processing circuit further comprises an analog-to-digital converter (ADC) circuit downstream from the amplifier, the ADC circuit configured to convert the provided signals into the digital samples.

15. The apparatus of claim 13 wherein the signal processing circuit further comprises a time-to-digital converter (TDC) circuit downstream from the amplifier, the TDC circuit configured to convert the provided signals into the digital samples.

16. The apparatus of claim 1 wherein the signal processing circuit comprises a field programmable gate array (FPGA), the FPGA configured to compute the range information based on the digital samples.

17. The apparatus of claim 16 wherein the FPGA is further configured to perform interpolation on the digital samples to compute the range information.

18. The apparatus of claim 1 wherein the light sensors of the array correspond to a plurality of pixels, and wherein the subsets of selected light sensors change over time with respect to how many pixels are included in the subsets.

19. The apparatus of claim 1 wherein the light sensors of the array correspond to a plurality of pixels, and wherein a plurality of the pixels exhibit a hexagonal shape.

20. The apparatus of claim 19 wherein a plurality of the pixels exhibit different sizes.

21. The apparatus of claim 1 wherein the light sensors of the array correspond to a plurality of pixels, and wherein a plurality of the pixels exhibit different sizes.

22. The apparatus of claim 1 further comprising a photodetector that is positioned optically downstream from the scanning ladar transmitter, wherein the photodetector comprises a region that is positioned to receive (1) the ladar pulses from the scanning ladar transmitter, and (2) light from the scanning ladar transmitter that is at a different frequency than the ladar pulses, and wherein the region is configured to pass the ladar pulses but absorb and convert the light at the different frequency into an output signal; and
wherein the circuit is further configured to track where the scanning ladar transmitter is targeted based on the output signal from the photodetector.

23. The apparatus of claim 22 wherein the circuit is further configured to selectively define the subsets of light sensors based on the tracking of where the scanning ladar transmitter is targeted when ladar pulses are transmitted.

24. The apparatus of claim 1 wherein the array is further positioned to receive, via an optical path that is distinct from an optical path traveled by the ladar pulses from a scanning ladar transmitter to the array, a reference light from the scanning ladar transmitter for timing coordination with respect to the ladar pulses such that the produced signal includes a portion attributable to a reflected ladar pulse and a portion attributable to the reference light; and
wherein

Assignees

• Aeye Inc

Inventors

• Dussan Luis Carlos
• Steinhardt Allan
• Cook David

Classifications

• G01S17/66

  Tracking systems using electromagnetic waves other than radio waves · CPC title

• G01S17/26

  wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals · CPC title

• G01S7/487

  Extracting wanted echo signals {, e.g. pulse detection} · CPC title

• G01S7/4865

  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 title

• G01S7/4863 Primary

  Detector arrays, e.g. charge-transfer gates · CPC title