Lidar system

• US 10,012,732 B2
• Filed: 12/29/2017
• Issued: 07/03/2018
• 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.
• Primary Examiner(s): Abraham, Samantha K
• Application Number:
  US15/859,170
• Publication Number:
  US 20180120433A1
• Time in Patent Office: 186 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 pulsed laser diode to produce a plurality of optical seed pulses of light at one or more operating wavelengths between approximately 1400 nm and approximately 1600 nm. The lidar system may also include one or more optical amplifiers to amplify the optical seed pulses to produce a plurality of output optical pulses. Each optical amplifier may produce an amount of amplified spontaneous emission (ASE), and the output optical pulses may have characteristics comprising: a pulse repetition frequency of less than or equal to 100 MHz; a pulse duration of less than or equal to 20 nanoseconds; and a duty cycle of less than or equal to 1%. The lidar system may also include one or more optical filters to attenuate the ASE and a receiver to detect at least a portion of the output optical pulses scattered by a target located a distance.

Claims

1. A lidar system comprising:

a pulsed laser diode configured to produce a plurality of optical seed pulses of light at one or more operating wavelengths between approximately 1400 nm and approximately 1600 nm;

one or more optical amplifiers configured to amplify the optical seed pulses to produce a plurality of output optical pulses, wherein each optical amplifier produces an amount of amplified spontaneous emission (ASE), and the output optical pulses have characteristics comprising;

a pulse repetition frequency of less than or equal to 100 MHz;

a pulse duration of less than or equal to 20 nanoseconds; and

a duty cycle of less than or equal to 1%;

one or more optical filters, wherein each optical filter is configured to transmit light at the one or more operating wavelengths and attenuate the ASE produced by one or more of the optical amplifiers; and

a receiver configured to detect at least a portion of the output optical pulses scattered by a target located a distance from the lidar system.

2. The lidar system of claim 1, wherein:

the optical amplifiers comprise a first optical amplifier configured to amplify the optical seed pulses and a second optical amplifier configured to receive and further amplify the optical pulses from the first amplifier; and

the optical filters comprise a first optical filter located between the first and second optical amplifiers and configured to transmit the optical pulses from the first amplifier and attenuate the ASE produced by the first optical amplifier.

3. The lidar system of claim 2, wherein:

the optical amplifiers further comprise a third optical amplifier configured to receive and further amplify the optical pulses from the second amplifier; and

the optical filters further comprise a second optical filter located between the second and third optical amplifiers and configured to transmit the optical pulses from the second amplifier and attenuate the ASE produced by the second optical amplifier.

4. The lidar system of claim 1, wherein the optical amplifiers comprise an optical amplifier configured to be disabled when an amount of light coming into the optical amplifier drops below a particular threshold level.

5. The lidar system of claim 4, wherein disabling the optical amplifier comprises reducing an amount of light produced by a pump laser of the optical amplifier.

6. The lidar system of claim 4, further comprising a photodiode configured to monitor the amount of light coming into the optical amplifier, wherein the amount of light dropping below the particular threshold level comprises an electrical signal produced by the photodiode dropping below a particular threshold voltage or current, wherein the electrical signal corresponds to the amount of light coming into the optical amplifier.

7. The lidar system of claim 1, further comprising a controller configured to:

detect a fault condition indicating a problem with the lidar system; and

in response to detecting the fault condition, shut down the optical amplifiers or reduce an amount of power of the output optical pulses.

8. The lidar system of claim 7, wherein the fault condition comprises:

a failure of a scanner of the lidar system;

a failure of the receiver;

or

a person or object coming within a threshold distance of the lidar system.

9. The lidar system of claim 1, wherein each of the optical filters is configured to attenuate the ASE produced by one of the optical amplifiers by at least 10 dB.

10. The lidar system of claim 1, wherein the characteristics of the output optical pulses further comprise:

a pulse energy of greater than or equal to 10 nanojoules;

a peak power of greater than or equal to 1 watt; and

an average power of less than or equal to 50 watts, wherein less than 25% of the average power comprises ASE from one or more of the optical amplifiers.

11. The lidar system of claim 1, wherein the pulsed laser diode is configured to be electrically driven by a pulse generator to produce the optical seed pulses of light.

12. The lidar system of claim 1, further comprising a scanner configured to scan the output optical pulses across a field of regard of the lidar system.

13. The lidar system of claim 12, wherein the scanner comprises:

a first mirror driven by a first galvanometer scanner that scans the output optical pulses along a first direction; and

a polygonal scanner that scans the output optical pulses along a second direction substantially orthogonal to the first direction.

14. The lidar system of claim 1, further comprising a processor configured to determine the distance from the lidar system to the target based at least in part on a round-trip time of flight for one of the output optical pulses to travel from the lidar system to the target and back to the lidar system.

15. 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.

16. The lidar system of claim 1, further comprising an output collimator configured to receive the output optical pulses from the optical amplifiers and produce a free-space optical beam comprising the output optical pulses.

17. The lidar system of claim 1, wherein each optical amplifier comprises a gain fiber and one or more pump lasers, wherein each pump laser has an operating wavelength of approximately 908 nm, 915 nm, 940 nm, 960 nm, 976 nm, 980 nm, 1050 nm, 1064 nm, 1450 nm, or 1480 nm.

18. The lidar system of claim 1, wherein the optical amplifiers comprise a single-pass amplifier comprising a gain fiber with erbium dopants or erbium and ytterbium dopants.

19. The lidar system of claim 1, wherein the optical amplifiers comprise a double-pass amplifier comprising:

a circulator;

an erbium-doped or erbium/ytterbium-doped gain fiber comprising a first end and a second end, wherein the first end is coupled to the circulator; and

a fiber Bragg grating (FBG) coupled to the second end of the gain fiber, wherein the FBG is configured to reflect light corresponding to the one or more operating wavelengths and transmit or attenuate light that is away from the reflected wavelengths.

20. The lidar system of claim 1, wherein the optical amplifiers comprise a booster amplifier comprising a double-clad gain fiber having erbium dopants or erbium and ytterbium dopants.