Methods and Apparatus for Array Based Lidar Systems with Reduced Interference

• US 20150131080A1
• Filed: 11/12/2013
• Published: 05/14/2015
• Est. Priority Date: 11/12/2013
• Status: Active Grant

• Current Assignee: SOS LAB Co., Ltd.
• Original Assignee: Facet Technology Corp.
• Inventors: Retterath, Jamie E., Laumeyer, Robert A.
• Granted Patent: US 10,203,399 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• 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 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/93 for anti-collision purposes
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4815 using multiple transmitters
• 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

Abstract

An array-based light detection and ranging (LiDAR) unit includes an array of emitter/detector sets configured to cover a field of view for the unit. Each emitter/detector set emits and receives light energy on a specific coincident axis unique for that emitter/detector set. A control system coupled to the array of emitter/detector sets controls initiation of light energy from each emitter and processes time of flight information for light energy received on the coincident axis by the corresponding detector for the emitter/detector set. The time of flight information provides imaging information corresponding to the field of view. Interference among light energy is reduced with respect to detectors in the LiDAR unit not corresponding to the specific coincident axis, and with respect to other LiDAR units and ambient sources of light energy. In one embodiment, multiple array-based LiDAR units are used as part of a control system for an autonomous vehicle.

Claims

1. An array-based light detection and ranging (LiDAR) unit comprising:

an array of emitter/detector sets configured to cover a field of view for the unit, each emitter/detector set configured to emit and receive light energy on a specific coincident axis unique for that emitter/detector set; and

a control system coupled to the array of emitter/detector sets to control initiation of light energy from each emitter and to process time of flight information for light energy received on the coincident axis by the corresponding detector for the emitter/detector set,

wherein time of flight information for light energy corresponding to the array of emitter/detector sets provides imaging information corresponding to the field of view for the unit and interference among light energy corresponding to an emitter of the specific coincident axis of an emitter/detector set is reduced with respect to detectors in the LiDAR unit other than the detector of the emitter/detector set corresponding to the specific coincident axis.

2. The array-based LiDAR unit of claim 1, wherein the control system initiates a multi-bit sequence of emitter pulses unique for the LiDAR unit that is used by the control system to reduce interference from other devices that are transmitting or reflecting energy at a target wavelength of the emitters of the LiDAR unit.

3. The array-based LiDAR unit of claim 2, wherein the control system initiates a multi-bit sequence of emitter pulses unique for each emitter in the array.

4. The array-based LiDAR unit of claim 3, wherein the multi-bit sequence of emitter pulses is unique for each emitter/detector cycle.

5. The array-based LiDAR unit of claim 1, wherein the array comprises a non-scanning, solid-state device having a multitude of emitter/detector sets arranged on a generally planer surface.

6. The array-based LiDAR unit of claim 5, wherein a number of emitter/detector sets ranges from a 16×

16 array of emitter/detector sets to an array of 4096×

4096 emitter/detector sets.

7. The array-based LiDAR unit of claim 1, wherein each emitter/detector set is a single pair of an emitter and a detector.

8. The array-based LiDAR unit of claim 1, wherein a single emitter is optically configured to provide on-coincident axis light energy to multiple different detectors, with each unique on-coincident axis combination of the single emitter and one micro-lens for that emitter and a plurality of different detectors each associated with a different detector micro-lens, each common emitter and unique detector comprising a different emitter/detector set.

9. The array-based LiDAR unit of claim 1, wherein the control system comprises:

a pulse generation controller configured to transmit a sequence of pulses from each of the emitters; and

a control unit configured to compute a time of flight measurement for light energy received at each of the corresponding on-coincident axis detectors.

10. The array-based LiDAR unit of claim 9, wherein the control unit includes a microprocessor unit (MPU) coupled to an output of at least one detector, the MPU being configured to analyze the light energy based on the output of the at least one detector.

11. The array based LiDAR unit of claim 10, wherein each emitter/detector set has a corresponding MPU unique to the emitter/detector set, and wherein the control system further comprises a processor coupled to each MPU to analyze information from the array of emitter/detector sets.

12. The array-based LiDAR unit of claim 9, wherein an output signal of the detector comprises an output signal of a detector shift register.

13. The array-based LiDAR unit of claim 1, wherein the field of view of the LiDAR unit is predetermined based on the optic configuration associated with each of the sets of emitter/detectors.

14. The array-based LiDAR unit of claim 13, wherein the macro field of view of the LiDAR unit is established upon fabrication of a micro-lens array together with the array of emitter/detector sets comprising a non-scanning, solid-state device having a multitude of emitter/detector sets arranged on a generally planer surface to establish the unique on-coincident axis associated with each emitter/detector set.

15. The array-based LiDAR unit of claim 13, wherein the macro field of view is established by a global lensing arrangement that is adjustable and optically coupled with a non-scanning, solid-state device having a multitude of emitter/detector sets arranged on a generally planer surface.

16. The array-based LiDAR unit of claim 13, wherein each emitter/detector set includes an optical waveguide through which the received light energy is directed for the on-coincident axis for that emitter/detector set.

17. The array-based LiDAR unit of claim 11, wherein the light energy is emitted and received as collimated electromagnetic energy.

18. The array-based LiDAR unit of claim 11, wherein the light energy is selected from the wavelength ranges of:

ultraviolet (UV)—

100-400 nm, visible—

400-700 nm, near infrared (NIR)—

700-1400 nm, infrared (IR)—

1400-8000 nm, long-wavelength IR (LWIR)—

8 um-15 um, or far IR (FIR)—

15 um-1000 um.

19. The array-based LiDAR unit of claim 10, wherein the MPU is configured to analyze the light energy based on an output of the detector of a given emitter/detector set and at least one secondary detector corresponding to the given emitter/detector set.

20. The array-based LiDAR unit of claim 19, wherein the at least one secondary detector includes a plurality of detectors in a concentric ring surrounding the given emitter/detector set in the array.

21. The array-based LiDAR unit of claim 20, wherein the MPU is further configured to analyze the light energy based on an output of at least a plurality of tertiary detectors corresponding to detectors in a second concentric ring surrounding the concentric ring formed by the at least one secondary detector.

22. The array-based LiDAR unit of claim 9, wherein the pulse generation circuit initiates generation of the emitted light energy as a pulse train for each emitter of the emitter/detector sets.

23. The array-based LiDAR unit of claim 22 wherein the pulse generation circuit includes at least one emitter shift register coupled to an input of each emitter, the emitter shift register being configured to activate at least one emitter based on an output of the at least one emitter shift register in response to an emitter clocking signal.

24. The array-based LiDAR unit of claim 23 wherein at least one detector shift register coupled to an output of each detector, the detector shift register being configured to be read by the control unit in response to a detector clocking signal.

25. The array-based LiDAR unit of claim 24, wherein the array comprises a non-scanning, solid-state device having m×

n emitter/detector sets, and wherein the control unit will compute the time of flight for a given sequence m,n upon completion of a sequence of emitting and detecting the pulse train and reading of the shift registers for element m,n, as;

t(flight)_m,n=λ

_detector*(k_m,n−

K_m,n)−

t_emitter−

t_detector

where

λ

_detector is a period of the detector clocking signal

k_m,n is a detector counter value for detector m,n when a detector match circuitry is triggered for element m,n

K is a number of bits in the detector shift register for element m,n

t_emitter is a delay from energizing of the emitter clock signal to energizing of the emitter

t_detector is a delay from photons reaching the detector to energizing of the circuitry at an input of the detector shift register.

26. A light detection and ranging (LiDAR) system for use with a vehicle comprising:

at least four array-based light detection and ranging (LiDAR) units, each LiDAR unit including;

an array of emitter/detector sets configured to cover a field of view for the LiDAR unit, each emitter/detector set configured to emit and receive light energy on a specific coincident axis unique for that emitter/detector set; and

a control system coupled to the array of emitter/detector sets to control initiation of light energy from each emitter and to process time of flight information for light energy received on the coincident axis by the corresponding detector for the emitter/detector set,

wherein time of flight information for light energy corresponding to the array of emitter/detector sets provides imaging information corresponding to the field of view for the LiDAR unit and interference with light energy other than that corresponding to an emitter of the specific coincident axis of an emitter/detector set is reduced,

wherein at least one LiDAR unit is configured as a long-range device having a narrower field of view configured for forward mapping and object identification in a direction of travel, at least one LiDAR unit is configured as a long-range device having a narrower field of view configured for backward mapping and object identification in the direction of travel, and at least two LiDAR units are configured as short-range devices having a wider field of view configured for sideways mapping of adjacent roadway information and object identification and determination of obstacles and vehicles not within the direction of travel.

27. The LiDAR system of claim 26, wherein the array of each LiDAR unit comprises a non-scanning, solid-state device having a multitude of emitter/detector sets arranged on a generally planer surface.

28. The LiDAR system of claim 27, wherein the field of view of each LiDAR unit is predetermined based on the optic configuration associated with each of the sets of emitter/detectors for that LiDAR unit and a macro field of view of the LiDAR unit is established upon fabrication of a micro-lens array together with the array of emitter/detector sets of the solid-state device.

29. The LiDAR system of claim 26, wherein the control system initiates a multi-bit sequence of emitter pulses unique for each emitter in the LiDAR unit that is used by the control system to reduce interference from other devices that are transmitting or reflecting energy at a target wavelength of the emitters of that LiDAR unit.

30. The LiDAR system of claim 29, wherein the control system of each LiDAR unit includes a pulse generation controller configured to transmit the multi-bit sequence of emitter pulses and a microprocessor unit (MPU) coupled to an output of at least one detector configured to compute at least a time of flight measurement for light energy received at each of the corresponding on-coincident axis detectors, wherein each emitter/detector set has a corresponding MPU unique to the emitter/detector set, and wherein the control system further comprises a processor coupled to each MPU to analyze information from the array of emitter/detector sets for that LiDAR unit.

31. The LiDAR system of claim 30, wherein, the pulse generation circuit initiates generation of the emitted light energy as a pulse train for each emitter of the emitter/detector sets of that LiDAR unit and includes at least one emitter shift register coupled to an input of each emitter, the emitter shift register being configured to activate at least one emitter based on an output of the at least one emitter shift register in response to an emitter clocking signal, and at least one detector shift register coupled to an output of each detector, the detector shift register being configured to be read by the MPU in response to a detector clocking signal.

32. The LiDAR system of claim 31, wherein each MPU compute the time of flight for a given sequence m,n upon completion of a sequence of emitting and detecting the pulse train and reading of the shift registers for element m,n, as;

t(flight)_m,n=λ

_detector*(k_m,n−

K_m,n)−

t_emitter−

t_detector

where

λ

_detector is a period of the detector clocking signal

k_m,n is a detector counter value for detector m,n when a detector match circuitry is triggered for element m,n

K is a number of bits in the detector shift register for element m,n

t_emitter is a delay from energizing of the emitter clock signal to energizing of the emitter

t_detector is a delay from photons reaching the detector to energizing of the circuitry at an input of the detector shift register.

33. A method of automatically operating light detection and ranging (LiDAR) device, the LiDAR device comprised of an array of emitter/detector sets configured to cover a field of view for the LiDAR device, comprising:

for each emitter/detector set in the array, using a control system to;

control initiation of light energy from the emitter on a specific coincident axis unique for that emitter/detector set; and

process time of flight information for light energy received on the coincident axis by the corresponding detector for the emitter/detector set,

wherein time of flight information for light energy corresponding to the array of emitter/detector sets provides imaging information corresponding to the field of view for the LiDAR unit and interference with light energy other than that corresponding to an emitter of the specific coincident axis of an emitter/detector set is reduced.

34. The method of claim 33, wherein the control system controls initiation of a multi-bit sequence of emitter pulses unique for each emitter in the LiDAR device that is used by the control system to reduce interference from other devices that are transmitting or reflecting energy at a target wavelength of the emitters of that LiDAR device.

35. The method of claim 34, wherein the control system transmits the multi-bit sequence of emitter pulses and computes at least a time of flight measurement for light energy received at each of the corresponding on-coincident axis detectors.

36. The method of claim 35, wherein, the control system initiates generation of the emitted light energy as a pulse train for each emitter of the emitter/detector sets and includes at least one emitter shift register coupled to an input of each emitter, the emitter shift register being configured to activate at least one emitter based on an output of the at least one emitter shift register in response to an emitter clocking signal, and at least one detector shift register coupled to an output of each detector, the detector shift register being configured to be read by a microprocessor unit (MPU) unique to that emitter./detector set in response to a detector clocking signal.

37. The method of claim 36, wherein each MPU computes the time of flight for a given sequence m,n upon completion of a sequence of emitting and detecting the pulse train and reading of the shift registers for element m,n, as;

t(flight)_m,n=λ

_detector*(k_m,n−

K_m,n)−

t_emitter−

t_detector

where

λ

_detector is a period of the detector clocking signal

k_m,n is a detector counter value for detector m,n when a detector match circuitry is triggered for element m,n

K is a number of bits in the detector shift register for element m,n

t_emitter is a delay from energizing of the emitter clock signal to energizing of the emitter

t_detector is a delay from photons reaching the detector to energizing of the circuitry at an input of the detector shift register.