LIDAR SYSTEM

• US 20170299721A1
• Filed: 03/27/2017
• Published: 10/19/2017
• Est. Priority Date: 11/30/2015
• Status: Active Grant

• Current Assignee: Luminar Technologies, Inc.
• Original Assignee: Luminar Technologies, Inc.
• Inventors: Eichenholz, Jason M., Russell, Austin K., Campbell, Scott R., Villeneuve, Alain, Cleye, Rodger W., LaChapelle, Joseph G., Weed, Matthew D., Martin, Lane A.
• Granted Patent: US 9,823,353 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 17/00 Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
• CPC Class Codes: G01S 17/02 Systems using the reflection of electromagnetic waves other than radio waves G01S17/66 takes precedence
• CPC Class Codes: G01S 17/06 Systems determining position data of a target
• 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 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
• 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 17/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4804 Auxiliary means for detecting or identifying lidar signals or the like, e.g. laser illuminators
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G01S 7/4814 of transmitters alone
• CPC Class Codes: G01S 7/4815 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 7/483 Details of pulse systems
• 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 7/4863 : 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 7/4873 : by deriving and controlling a threshold value
• CPC Class Codes: G01S 7/4876 : by removing unwanted signals G01S7/495 takes precedence
• CPC Class Codes: H01S 2301/02 : ASE (amplified spontaneous emission), noise; Reduction thereof
• CPC Class Codes: H01S 3/0007 : Applications not otherwise provided for working metals or other materials by laser beam B23K26/00; using photons to produce a reactive propulsive thrust F03H3/00; optical recording of measured values in general G01D15/14; optics in general G02B; holographic processes or apparatus G03H; optical marking or sensing of data record carriers G06K7/10 - G06K7/14, G06K15/12; injection heating of plasma by laser H05H1/22; acceleration of neutral particles by electromagnetic wave pressure H05H3/04
• CPC Class Codes: H01S 3/0078 : Frequency filtering
• CPC Class Codes: H01S 3/0085 : Modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 3/06733 : Fibre having more than one cladding
• CPC Class Codes: H01S 3/0675 : Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/06754 : Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/06758 : Tandem amplifiers
• CPC Class Codes: H01S 3/08086 : Multiple-wavelength emission
• CPC Class Codes: H01S 3/094003 : the pumped medium being a fibre
• CPC Class Codes: H01S 3/094042 : of a fibre laser
• CPC Class Codes: H01S 3/094076 : Pulsed or modulated pumping H01S3/1024 takes precedence
• CPC Class Codes: H01S 3/0941 : of a laser diode
• CPC Class Codes: H01S 3/10023 : by functional association of additional optical elements, e.g. filters, gratings, reflectors
• CPC Class Codes: H01S 3/1106 : Mode locking
• CPC Class Codes: H01S 3/1608 : erbium
• CPC Class Codes: H01S 3/2383 : Parallel arrangements
• CPC Class Codes: H01S 5/0057 : for temporal shaping, e.g. pulse compression, frequency chirping
• CPC Class Codes: H01S 5/0085 : for modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 5/4012 : Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4087 : emitting more than one wavelength

Abstract

A lidar system with a light source to emit a pulse of light into a field of view and a receiver to detect a return pulse of light which is reflected or scattered by a target in the field of view. The receiver may include an avalanche photodiode to generate an electrical-current pulse corresponding to the return pulse and a transimpedance amplifier to produce a voltage pulse that corresponds to the electrical-current pulse. A voltage amplifier may amplify the voltage pulse and a comparator may produce an edge signal when the amplified voltage pulse exceeds a threshold. A time-to-digital converter may determine a time interval based on an emission time of the pulse of light and based on the edge signal. A processor may determine a distance to the target using the time interval.

Claims

1. A lidar system comprising:

a light source configured to emit a pulse of light into a field of view;

a receiver configured to detect a return pulse of light which comprises at least a portion of the emitted pulse of light which is reflected or scattered by a target in the field of view, the receiver comprising

an avalanche photodiode configured to generate an electrical-current pulse corresponding to the return pulse of light,

a transimpedance amplifier configured to produce a voltage pulse that corresponds to the electrical-current pulse,

a voltage amplifier configured to amplify the voltage pulse to produce an amplified voltage pulse,

a first comparator configured to produce a first edge signal when the amplified voltage pulse exceeds a first threshold, and

a time-to-digital converter configured to determine a first time interval based on an emission time of the pulse of light and based on the first edge signal; and

a processor configured to determine a distance to the target using the first time interval.

2. The lidar system of claim 1, further comprising a sensor head located remotely from the light source, wherein:

the sensor head comprises the receiver; and

the sensor head is coupled to the light source by an optical link.

3. The lidar system of claim 2, wherein the lidar system further comprises one or more additional sensor heads, wherein:

each of the additional sensor heads comprises a respective receiver; and

the light source is coupled to each of the additional sensor heads by a respective optical link.

4. The lidar system of claim 3, wherein the lidar system is incorporated into a vehicle, and wherein the sensor head and the one or more additional sensor heads of the lidar system are positioned about the vehicle to provide at least a 180-degree view of an environment around the vehicle.

5. The lidar system of claim 1, wherein the lidar system has a horizontal resolution of at least 100 pixels and a vertical resolution of at least 4 pixels.

6. The lidar system of claim 1, wherein the lidar system is configured to generate point clouds of distance measurements at a rate between approximately 0.1 frames per second and approximately 1,000 frames per second.

7. The lidar system of claim 1, wherein:

the light source emits the pulse into a light source field of view;

the receiver detects the return pulse from a receiver field of view;

the light-source field of view and the receiver field of view are scanned along a scanning direction; and

the receiver field of view is offset from the light-source field of view in a direction opposite the scanning direction.

8. The lidar system of claim 1, wherein:

the light source emits the pulse into a light source field of view;

the receiver detects the return pulse from a receiver field of view; and

an angular extent of the light source field of view is approximately equal to an angular extent of the receiver field of view.

9. The lidar system of claim 1, wherein:

the light source emits the pulse into a light source field of view;

the receiver detects the return pulse from a receiver field of view;

the light-source field of view has an angular extent of less than or equal to 50 milliradians; and

the receiver field of view has an angular extent of less than or equal to 50 milliradians.

10. The lidar system of claim 1, wherein the time-to-digital converter is configured to determine the first time interval by determining a time associated with the emission of the pulse of light based at least in part on detection by the receiver of a portion of the emitted pulse of light.

11. The lidar system of claim 1, wherein the receiver further comprises:

a second comparator configured to produce a second edge signal when the amplified voltage pulse falls below a second threshold,

wherein the time-to-digital converter is configured to determine a second time interval based on the emission time of the pulse of light by the light source and based on the second edge signal.

12. The lidar system of claim 11, further comprising a processor configured to determine the distance to the target based at least in part on the first and second time intervals.

13. The lidar system of claim 1, further comprising an optical filter, wherein the optical filter is configured to transmit the return pulse and attenuate other light by at least 10 dB.

14. The lidar system of claim 1, wherein the receiver comprises an array of two or more avalanche photodiodes.

15. The lidar system of claim 1, wherein the receiver comprises:

an avalanche photodiode configured to operate as a single-photon avalanche diode (SPAD); and

a quenching circuit configured to reduce a reverse-bias voltage applied to the SPAD when an avalanche event occurs in the SPAD.

16. The lidar system of claim 1, wherein the receiver comprises:

two or more avalanche photodiodes (APDs); and

one or more logic gates coupled to the APDs, wherein the logic gates are configured to produce an output indicating that the receiver has detected the return pulse only if each of the APDs produces an electrical signal corresponding to detection of the return pulse.

17. The lidar system of claim 1, wherein the processor is configured to determine the distance to the target based at least in part on a round-trip time of flight for the pulse of light emitted by the light source to travel from the lidar system to the target and back to the lidar system.

18. The lidar system of claim 17, wherein the round-trip time of flight is determined based at least in part on a rising edge or a falling edge associated with the return pulse of light detected by the receiver.

19. The lidar system of claim 1, further comprising a plurality of comparators, the plurality of comparators being configured to determine when the amplified voltage pulse reaches a respective plurality of different reference values so as to provide information about the shape of the amplified voltage pulse.